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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2013	Feb. 28, 2014	Jun. 30, 2013
Entity Registrant Name	Summit Midstream Partners, LP
Entity Central Index Key	0001549922
Document Type	10-K
Document Period End Date	Dec. 31, 2013
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 495,695,516
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Common units
Entity Common Stock, Shares Outstanding		29,079,866
Subordinated Units
Entity Common Stock, Shares Outstanding		24,409,850
General Partner Units
Entity Common Stock, Shares Outstanding		1,091,453

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 18,764	$ 7,895
Accounts receivable	54,256	33,504
Due from affiliate	0	774
Other assets	3,089	2,190
Total current assets	76,109	44,363
Property, plant and equipment, net	980,341	681,993
Intangible assets, net:
Favorable gas gathering contracts	17,880	19,958
Contract intangibles	383,306	229,596
Rights-of-way	51,808	35,986
Total intangible assets, net	452,994	285,540
Goodwill	115,888	45,478
Other noncurrent assets	14,583	6,137
Total assets	1,639,915	1,063,511
Current liabilities:
Trade accounts payable	18,132	15,817
Due to affiliate	653	0
Deferred revenue	1,555	865
Ad valorem taxes payable	6,804	5,455
Accrued interest	12,144	16
Other current liabilities	9,055	4,308
Total current liabilities	48,343	26,461
Long-term debt	586,000	199,230
Noncurrent liability, net (Note 4)	6,374	7,420
Deferred revenue	29,683	10,899
Other noncurrent liabilities	372	254
Total liabilities	670,772	244,264
Commitments and contingencies (Note 12)
Common limited partner capital (29,079,866 units issued and outstanding at December 31, 2013 and 24,412,427 units issued and outstanding at December 31, 2012)	566,532	418,856
Subordinated limited partner capital (24,409,850 units issued and outstanding at December 31, 2013 and 2012)	379,287	380,169
General partner interests (1,091,453 units issued and outstanding at December 31, 2013 and 996,320 issued and outstanding at December 31, 2012)	23,324	20,222
Total partners' capital	969,143	819,247
Total liabilities and partners' capital	$ 1,639,915	$ 1,063,511

CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Dec. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Common limited partner capital, units issued	29,079,866	24,412,427
Common limited partner capital, units outstanding	29,079,866	24,412,427
Subordinated limited partner capital, units issued	24,409,850	24,409,850
Subordinated limited partner capital, units outstanding	24,409,850	24,409,850
General partner interests, units issued	1,091,453	996,320
General partner interests, units outstanding	1,091,453	996,320

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Gathering services and other fees	$ 174,506	$ 149,371	$ 91,421
Natural gas, NGLs and condensate sales and other	69,332	16,320	12,439
Amortization of favorable and unfavorable contracts	(1,032)	(192)	(308)
Total revenues	242,806	165,499	103,552
Costs and expenses:
Operation and maintenance	59,972	51,658	29,855
Cost of natural gas and NGLs	31,036	0	0
General and administrative	24,558	21,357	17,476
Transaction costs	2,770	2,020	3,166
Depreciation and amortization	60,824	35,299	11,367
Total costs and expenses	179,160	110,334	61,864
Other (expense) income	(108)	9	12
Interest expense	(19,173)	(7,340)	(1,029)
Affiliated interest expense	0	(5,426)	(2,025)
Income before income taxes	44,365	42,408	38,646
Income tax expense	(729)	(682)	(695)
Net income	43,636	41,726	$ 37,951
Less: net income attributable to the pre-IPO period	0	24,112
Less: net income attributable to SMP Holdings (Note 1)	52	0
Net income attributable to SMLP	43,584	17,614
Less: net income attributable to general partner, including IDRs	1,035	352
Net income attributable to limited partners	$ 42,549	$ 17,262
Earnings per common unit – basic (in dollars per unit)	$ 0.86	$ 0.35
Earnings per common unit – diluted (in dollars per unit)	0.86	0.35
Earnings per subordinated unit – basic and diluted (in dollars per unit)	$ 0.79	$ 0.35
Weighted-average common units outstanding – basic (in units)	26,951,346	24,412,427
Weighted-average common units outstanding – diluted (in units)	27,101,479	24,543,985
Weighted-average subordinated units outstanding – basic and diluted (in units)	24,409,850	24,409,850

CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS - USD ($) $ in Thousands	Total	Bison Midstream	Mountaineer Midstream	SMLP units	Class B Units	SMP Holdings' equity in Bison Midstream	SMP Holdings' equity in Bison Midstream Bison Midstream	Membership interests	Membership interests Class B Units	Limited partners, Common	Limited partners, Common Bison Midstream	Limited partners, Common SMLP units	Limited partners, Common Class B Units	Limited partners, Subordinated	Limited partners, Subordinated Bison Midstream	General partner	General partner Bison Midstream	General partner Mountaineer Midstream
Beginning balance at Dec. 31, 2010	$ 307,370					$ 0		$ 307,370		$ 0				$ 0		$ 0
Members Interest Increase (Decrease) Abstract
Net income	37,951							37,951
Unit-based compensation					$ 3,440				$ 3,440
Net assets retained by the Predecessor	0
Contributions from Sponsors	425,000							425,000
Contribution of net assets from SMP Holdings in excess of consideration paid for Bison Midstream	0
Distributions to unitholders	(132,943)							(132,943)
Ending balance at Dec. 31, 2011	640,818					0		640,818		0				0		0
Members Interest Increase (Decrease) Abstract
Net income	41,726							24,112		8,631				8,631		352
Unit-based compensation				$ 269	1,607				$ 1,793			$ 269	$ (186)
Net assets retained by the Predecessor	(4,417)							(4,417)
Contributions from Sponsors	0							(662,306)		211,938				430,498		19,870
Contribution of net assets from SMP Holdings in excess of consideration paid for Bison Midstream	0
Issuance of common units, net of offering costs	262,382									262,382
Distributions to unitholders	(123,138)									(64,178)				(58,960)
Ending balance at Dec. 31, 2012	819,247					0		0		418,856				380,169		20,222
Members Interest Increase (Decrease) Abstract
Net income	43,636					52				22,311				20,238		1,035
Unit-based compensation				$ 2,999	$ 17							$ 2,999	$ 17
Net assets retained by the Predecessor	0
Consolidation of Bison Midstream net assets		$ 303,168					$ 303,168
Contribution from SMP Holdings to Bison Midstream		2,229					2,229
Units issued to acquire entity		(200,000)	$ 100,000				(248,914)				$ 47,936						$ 978	$ 2,000
Contribution of net assets from SMP Holdings in excess of consideration paid for Bison Midstream	56,535	$ 0					$ (56,535)				$ 28,558				$ 26,846		$ 1,131
Repurchase of DFW Net Profits Interests	(11,957)									(5,859)				(5,859)		(239)
Distributions to unitholders	(90,196)									(46,286)				(42,107)		(1,803)
Ending balance at Dec. 31, 2013	$ 969,143					$ 0		$ 0		$ 566,532				$ 379,287		$ 23,324

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 43,636	$ 41,726	$ 37,951
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	61,856	35,491	11,675
Amortization of deferred loan costs	2,246	1,458	560
Unit-based compensation	3,016	1,876	3,440
Loss on asset sales	113	0	0
Pay-in-kind interest on promissory notes payable to Sponsors	0	5,426	2,025
Changes in operating assets and liabilities:
Accounts receivable	(15,147)	(6,028)	(17,238)
Due to/from affiliate	1,427	(774)	0
Trade accounts payable	(1,992)	(2,164)	2,468
Change in deferred revenue	16,685	9,994	0
Ad valorem taxes payable	1,264	3,072	0
Accrued interest	12,128	(484)	500
Other, net	725	(105)	(1,439)
Net cash provided by operating activities	125,957	89,488	39,942
Cash flows from investing activities:
Capital expenditures	(81,911)	(76,698)	(78,248)
Proceeds from asset sales	585	0	0
Acquisition of gathering systems	(210,000)	0	(589,462)
Acquisition of gathering system from affiliate	(200,000)	0	0
Net cash used in investing activities	(491,326)	(76,698)	(667,710)
Cash flows from financing activities:
Distributions to unitholders	(90,196)	0	0
Borrowings under revolving credit facility	380,950	213,000	147,000
Repayments under revolving credit facility	(294,180)	(160,770)	0
Issuance of senior notes	300,000	0	0
Contribution from SMP Holdings to Bison Midstream	2,229	0	0
Issuance of units to affiliate in connection with the Mountaineer Acquisition	100,000	0	0
Proceeds from issuance of units	0	263,125	0
Repurchase of DFW Net Profits Interests	(11,957)	0	0
Deferred loan costs	(10,608)	(3,344)	(5,248)
Repayment of promissory notes payable to Sponsors	0	(209,230)	200,000
Distributions to Sponsors	0	(123,138)	(132,943)
Contributions from Sponsors	0	0	425,000
Net cash provided by (used in) financing activities	376,238	(20,357)	633,809
Net change in cash and cash equivalents	10,869	(7,567)	6,041
Cash and cash equivalents, beginning of period	7,895	15,462	9,421
Cash and cash equivalents, end of period	18,764	7,895	15,462
Supplemental Cash Flow Disclosures:
Cash interest paid	9,016	8,283	2,463
Less: capitalized interest	4,209	2,784	3,362
Interest paid (net of capitalized interest)	4,807	5,499	(899)
Cash paid for income taxes	660	650	223
Noncash Investing and Financing Activities:
Capital expenditures in trade accounts payable (period-end accruals)	10,245	7,829	11,332
Issuance of units to affiliate to partially fund the Bison Drop Down	48,914	0	0
Contribution of net assets from SMP Holdings in excess of consideration paid for Bison Midstream	56,535	0	0
Pay-in-kind interest on promissory notes payable to Sponsors	0	6,337	2,893
Net assets retained by the Predecessor	0	4,417	0
Deferred initial public offering costs in trade accounts payable	0	743	0
Working capital acquired related to Grand River system acquisition	$ 0	$ 0	$ 854

ORGANIZATION, BUSINESS OPERATIONS AND BASIS OF PRESENTATION

12 Months Ended

Dec. 31, 2013

Organization, Consolidation and Presentation of Financial Statements [Abstract]

ORGANIZATION, BUSINESS OPERATIONS AND BASIS OF PRESENTATION

Organization. Summit Midstream Partners, LP ("SMLP" or the "Partnership"), a Delaware limited partnership, was formed in May 2012 and began operations in October 2012 in connection with its initial public offering ("IPO") of common limited partner units. SMLP is a growth-oriented limited partnership focused on developing, owning and operating midstream energy infrastructure assets that are strategically located in the core producing areas of unconventional resource basins, primarily shale formations, in North America.

Effective with the completion of its IPO on October 3, 2012, SMLP has a 100% ownership interest in Summit Midstream Holdings, LLC ("Summit Holdings") which has a 100% ownership interest in both DFW Midstream Services LLC ("DFW Midstream") and Grand River Gathering, LLC ("Grand River Gathering"). The effects of the IPO and related equity transfers occurring in October 2012 are reflected in SMLP's financial statements. For additional information, see "—Initial Public Offering" below.

On June 4, 2013, Summit Holdings acquired all of the membership interests of Bison Midstream, LLC ("Bison Midstream") from Summit Midstream Partners Holdings, LLC ("SMP Holdings"), a wholly owned direct subsidiary of Summit Midstream Partners, LLC ("Summit Investments") (the "Bison Drop Down"), and thereby acquired certain associated natural gas gathering pipeline, dehydration and compression assets in the Bakken Shale Play in Mountrail and Burke counties in North Dakota (the "Bison Gas Gathering system").

Prior to the Bison Drop Down, on February 15, 2013, Summit Investments acquired Bear Tracker Energy, LLC ("BTE") and subsequently contributed it to SMP Holdings. The Bison Gas Gathering system was carved out from BTE in connection with the Bison Drop Down. As such, it was deemed a transaction among entities under common control. For additional information, see Notes 5, 6 and 13.

On June 21, 2013, Mountaineer Midstream Company, LLC ("Mountaineer Midstream"), a newly formed, wholly owned subsidiary of Summit Holdings, acquired certain natural gas gathering pipeline and compression assets in the Marcellus Shale Play in Doddridge County, West Virginia from an affiliate of MarkWest Energy Partners, L.P. ("MarkWest") (the "Mountaineer Acquisition"). In December 2013, Mountaineer Midstream was merged into DFW Midstream. For additional information, see Notes 5, 6 and 13.

Summit Investments is a Delaware limited liability company and the predecessor for accounting purposes (the "Predecessor") of SMLP. Summit Investments was formed and began operations in September 2009. Through August 2011, Summit Investments was wholly owned by Energy Capital Partners II, LLC and its parallel and co-investment funds (collectively, "Energy Capital Partners"). In August 2011, Energy Capital Partners sold an interest in Summit Investments to a subsidiary of GE Energy Financial Services, Inc. ("GE Energy Financial Services", and collectively with Energy Capital Partners, the "Sponsors"). In March 2013, Summit Investments contributed the ownership of its SMLP common and subordinated units along with its 2% general partner interest in SMLP to SMP Holdings in exchange for a continuing 100% interest in SMP Holdings. As of December 31, 2013, SMP Holdings held 14,691,397 SMLP common units, 24,409,850 SMLP subordinated units and 1,091,453 general partner units representing a 2% general partner interest in SMLP.

SMLP is managed and operated by the board of directors and executive officers of Summit Midstream GP, LLC (the "general partner"). Summit Investments, as the ultimate owner of our general partner, controls SMLP and has the right to appoint the entire board of directors of our general partner, including our independent directors. SMLP's operations are conducted through, and our operating assets are owned by, various operating subsidiaries. However, neither SMLP nor its subsidiaries has any employees. The general partner has the sole responsibility for providing the personnel necessary to conduct SMLP's operations, whether through directly hiring employees or by obtaining the services of personnel employed by others, including Summit Investments. All of the personnel that conduct SMLP's business are employed by the general partner and its affiliates, but these individuals are sometimes referred to as our employees.

References to the "Company," "we," or "our," when used for dates or periods ended on or after the IPO, refer collectively to SMLP and its subsidiaries. References to the "Company," "we," or "our," when used for dates or periods ended prior to the IPO, refer collectively to Summit Investments and its subsidiaries.

Initial Public Offering. On October 3, 2012, SMLP completed its IPO and the following transactions occurred:


•	Summit Investments conveyed an interest in Summit Midstream Holdings, LLC ("Summit Holdings") to our general partner as a capital contribution;


•	our general partner conveyed its interest in Summit Holdings to SMLP in exchange for (i) a continuation of its 2% general partner interest in SMLP, represented by 996,320 general partner units, and (ii) SMLP incentive distribution rights, or IDRs;

•

Summit Investments conveyed its remaining interest in Summit Holdings to SMLP in exchange for (i) 10,029,850 common units (net of the impact of selling 1,875,000 common units to the public for cash in connection with the exercise of the underwriters’ option to purchase additional common units), representing a 20.1% limited partner interest in SMLP, (ii) 24,409,850 subordinated units, representing a 49.0% limited partner interest in SMLP, and (iii) the right to receive $88.0 million in cash as reimbursement for certain capital expenditures made with respect to the contributed assets;


•	pursuant to its long-term incentive plan, SMLP granted 5,000 common units (in the aggregate) to two of its directors and 125,000 phantom units, with distribution equivalent rights, to certain employees;


•	SMLP issued 14,375,000 common units to the public (including 1,875,000 additional common units sold out of the common units originally allocated to Summit Investments) representing a 28.9% limited partner interest in SMLP; and

•

SMLP used the proceeds, net of underwriters’ fees, from the IPO of approximately $269.4 million to (i) repay $140.0 million outstanding under the revolving credit facility; (ii) make cash distributions to Summit Investments of (a) $88.0 million to reimburse Summit Investments for certain capital expenditures it incurred with respect to assets it contributed to us and (b) $35.1 million representing the funds received in connection with the underwriters exercising their option to purchase additional common units; and (iii) pay IPO expenses of approximately $6.3 million.

Business Operations. We provide natural gas gathering and compression services pursuant to long-term, primarily fee-based, natural gas gathering agreements with our customers. Our results are driven primarily by the volumes of natural gas that we gather and compress across our systems. Our gathering systems and the unconventional resource basins in which they operate as of December 31, 2013 were as follows:


•	Mountaineer Midstream – the Appalachian Basin, which includes the Marcellus Shale formation in northern West Virginia;


•	Bison Midstream – the Williston Basin, which includes the Bakken and Three Forks shale formations in northwestern North Dakota


•	DFW Midstream – the Fort Worth Basin, which includes the Barnett Shale formation in north-central Texas; and


•	Grand River Gathering – the Piceance Basin, which includes the Mesaverde formation and the Mancos and Niobrara shale formations in western Colorado.

Our operating subsidiaries are DFW Midstream (which includes the Mountaineer Midstream gathering system), Bison Midstream and Grand River Gathering. All of our operating subsidiaries are midstream energy companies focused on the development, construction and operation of natural gas gathering systems.

In October 2011, we acquired Grand River Gathering. Grand River Gathering owns certain natural gas gathering pipeline, dehydration and compression assets located in the Piceance Basin. These assets gather production from the Mamm Creek, Orchard, and South Parachute fields in the area around Rifle, Colorado. In addition to the purchase, we have a contractual relationship with the seller related to the development of midstream infrastructure to support the seller’s emerging Mancos and Niobrara shale developments.

DFW Midstream owns certain natural gas gathering pipeline and compression assets located in the Fort Worth Basin.

Basis of Presentation and Principles of Consolidation. We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the United States of America ("GAAP"). These principles are established by the Financial Accounting Standards Board. We make estimates and assumptions that affect the reported amounts of assets and liabilities at the balance sheet dates, including fair value measurements, the reported amounts of revenue and expense, and the disclosure of contingencies. Although management believes these estimates are reasonable, actual results could differ from its estimates.

For the purposes of the consolidated financial statements, SMLP's results of operations reflect the Partnership's operations subsequent to the IPO and the results of the Predecessor for the period prior to the IPO. The consolidated financial statements also reflect the results of operations of: (i) Bison Midstream since February 16, 2013 and (ii) Mountaineer Midstream since June 22, 2013. Because the Bison Drop Down was executed between entities under common control, SMLP recognized the acquisition of Bison Midstream at SMP Holdings' historical cost which reflected its fair value accounting for the acquisition of BTE. The excess of SMP Holdings' net investment in Bison Midstream over the purchase price paid by SMLP was recognized as an addition to partners' capital. Due to the common control aspect, the Bison Drop Down was accounted for by the Partnership on an “as if pooled” basis for the period during which common control existed. See Notes 5, 6 and 13 for additional information. The consolidated financial statements include the assets, liabilities, and results of operations of SMLP or the Predecessor and their respective wholly owned subsidiaries. All intercompany transactions among the consolidated entities have been eliminated in consolidation.

We conduct our operations in the midstream sector with four operating segments: Mountaineer Midstream, Bison Midstream, DFW Midstream and Grand River Gathering. However, due to their similar characteristics and how we manage our business, we have aggregated these segments into one reportable segment for disclosure purposes. The assets of our reportable segment consist of natural gas gathering systems and related plant and equipment. Our operating segments reflect the way in which we internally report the financial information used to make decisions and allocate resources in connection with our operations.

Reclassifications. Certain reclassifications have been made to prior-year amounts to conform to current-year presentation. These reclassifications had no impact on net income or total partners' capital or membership interests.

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

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+ Details

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Cash and Cash Equivalents. Cash and cash equivalents include temporary cash investments with original maturities of three months or less.

Accounts Receivable. Accounts receivable relate to gathering and other services provided to our natural gas producer customers. To the extent we doubt the collectability of our accounts receivable, we recognize an allowance for doubtful accounts. We did not experience any non-payments during the three-year period ended December 31, 2013. As a result, we did not recognize an allowance for doubtful accounts as of December 31, 2013 and 2012.

Property, Plant, and Equipment. We record property, plant, and equipment at historical cost of construction or fair value of the assets at acquisition. We capitalize expenditures that extend the useful life of an asset or enhance its productivity or efficiency from its original design over the expected remaining period of use. For maintenance and repairs that do not add capacity or extend the useful life of an asset, we recognize expenditures as an expense as incurred. We capitalize project costs incurred during construction, including interest on funds borrowed to finance the construction of facilities, as construction in progress.

We base an asset’s carrying value on estimates, assumptions and judgments for useful life and salvage value. We record depreciation on a straight-line basis over an asset’s estimated useful life. We base our estimates for useful life on various factors including age (in the case of acquired assets), manufacturing specifications, technological advances, and historical data concerning useful lives of similar assets.

Upon sale or retirement, we remove the carrying value of an asset and its accumulated depreciation from our balance sheet and recognize the related gain or loss, if any.

Asset Retirement Obligations. We record a liability for asset retirement obligations only if and when a future asset retirement obligation with a determinable life is identified. As of December 31, 2013 and 2012, we evaluated whether any future asset retirement obligations existed. For identified asset retirement obligations, we then evaluated whether the expected retirement date and the related costs of retirement could be estimated. In performing this evaluation, we concluded that our natural gas gathering system assets have an indeterminate life because they are owned and will operate for an indeterminate future period when properly maintained. Because we did not have sufficient information to reasonably estimate the amount or timing of such obligations and we have no current plan to discontinue use of any significant assets, we did not provide for any asset retirement obligations as of December 31, 2013 or 2012.

Intangible Assets and Noncurrent Liability. Upon the acquisition of DFW Midstream, certain of our gas gathering contracts were deemed to have above-market pricing structures while another was deemed to have pricing that was below market. We have recognized the contracts that were above market at acquisition as favorable gas gathering contracts. We have recognized the contract that was deemed to be below market as a noncurrent liability. We amortize these intangibles on a units-of-production basis over the estimated useful life of the contract. We define useful life as the period over which the contract is expected to contribute directly or indirectly to our future cash flows. The related contracts have original terms ranging from 10 years to 20 years. We recognize the amortization expense associated with these intangible assets and liabilities in revenue.

For our other gas gathering contracts, we amortize contract intangible assets over the period of economic benefit based upon the expected revenues over the life of the contract. The useful life of these contracts ranges from 10 years to 25 years. We recognize the amortization expense associated with these intangible assets in depreciation and amortization expense.

We have right-of-way intangible assets associated with city easements and easements granted within existing rights-of-way. We amortize these intangible assets over the shorter of the contractual term of the rights-of-way or the estimated useful life of the gathering system. The contractual terms of the rights-of-way range from 20 years to 30 years. The estimated useful life of our gathering systems is 30 years. We recognize the amortization expense associated with these intangible assets in depreciation and amortization expense.

Impairment of Long-Lived Assets. We test assets for impairment when events or circumstances indicate that the carrying value of a long-lived asset may not be recoverable. The carrying value of a long-lived asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from its use and eventual disposition. If we conclude that an asset’s carrying value will not be recovered through future cash flows, we recognize an impairment loss on the long-lived asset equal to the amount by which the carrying value exceeds its fair value. We determine fair value using an income approach in which we discount the asset’s expected future cash flows to reflect the risk associated with achieving the underlying cash flows. During the three-year period ended December 31, 2013, we concluded that none of our long-lived assets had been impaired.

Goodwill. Goodwill represents consideration paid in excess of the fair value of the net identifiable assets acquired in a business combination. We evaluate goodwill for impairment annually on September 30. We also evaluate goodwill whenever events or circumstances indicate that it is more likely than not that the fair value of a reporting unit is less than its carrying amount.

We test goodwill for impairment using a two-step quantitative test. In the first step, we compare the fair value of the reporting unit to its carrying value, including goodwill. If the reporting unit’s fair value exceeds its carrying amount, we conclude that the goodwill of the reporting unit has not been impaired and no further work is performed. If we determine that the reporting unit’s carrying value exceeds its fair value, we proceed to step two. In step two, we compare the carrying value of the reporting unit to its implied fair value. If we determine that the carrying amount of a reporting unit's goodwill exceeds its implied fair value, we recognize the excess of the carrying value over the implied fair value as an impairment loss.

Other Noncurrent Assets. Other noncurrent assets primarily consist of external costs incurred in connection with the issuance of our senior notes and the closing of our revolving credit facility and related amendments. We capitalize and then amortize these deferred loan costs over the life of the respective debt instrument. We recognize amortization of deferred loan costs in interest expense.

Derivative Contracts. We have commodity price exposure related to our sale of the physical natural gas we retain from our DFW customers, and our procurement of electricity to operate our electric-drive compression assets on the DFW Midstream system. Our gas gathering agreements with our DFW Midstream customers permit us to retain a certain quantity of natural gas that we gather to offset the power costs we incur to operate our electric-drive compression assets. We manage this direct exposure to natural gas and power prices through the use of forward power purchase contracts with wholesale power providers that require us to purchase a fixed quantity of power at a fixed heat rate based on prevailing natural gas prices on the Waha Hub Index. Because we also sell our retainage gas at prices that are based on the Waha Hub Index, we have effectively fixed the relationship between our compression electricity expense and natural gas retainage sales.

Accounting standards related to derivative instruments and hedging activities allow for "normal" purchase or sale elections and hedge accounting designations, which generally eliminate or defer the requirement for mark-to-market recognition in net income and thus reduce the volatility of net income that can result from fluctuations in fair values. We have designated these contracts as normal under the normal purchase and sale exception under the accounting standards for derivatives. We do not enter into risk management contracts for speculative purposes.

Fair Value of Financial Instruments. The carrying amount of cash and cash equivalents (Level 1), accounts receivable, and accounts payable reported on the balance sheet approximates fair value due to their short-term maturities.

GAAP's fair-value-measurement standard defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The standard characterizes inputs used in determining fair value according to a hierarchy that prioritizes those inputs based upon the degree to which they are observable. The three levels of the fair value hierarchy are as follows:


•	Level 1. Inputs represent quoted prices in active markets for identical assets or liabilities;

•

Level 2. Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly (for example, quoted market prices for similar assets or liabilities in active markets or quoted market prices for identical assets or liabilities in markets not considered to be active, inputs other than quoted prices that are observable for the asset or liability, or market-corroborated inputs); and


•	Level 3. Inputs that are not observable from objective sources, such as management’s internally developed assumptions used in pricing an asset or liability (for example, an estimate of future cash flows used in management’s internally developed present value of future cash flows model that underlies the fair value measurement).

Nonfinancial assets and liabilities initially measured at fair value include those acquired and assumed in connection with third-party business combinations.

A summary of the estimated fair value for financial instruments follows.



	December 31, 2013				December 31, 2012
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	286,000	$	286,000	$	199,230	$	199,230
Senior notes	300,000		314,625		—		—

The revolving credit facility’s carrying value on the balance sheet is its fair value due to its floating interest rate. The fair value for the senior notes is based on an average of nonbinding broker quotes as of December 31, 2013. The use of different market assumptions or valuation methodologies may have a material effect on the estimated fair value of the senior notes.

Commitments and Contingencies. We record accruals for loss contingencies when we determine that it is probable that a liability has been incurred and that such economic loss can be reasonably estimated. Such determinations are subject to interpretations of current facts and circumstances, forecasts of future events, and estimates of the financial impacts of such events.

Revenue Recognition. We generate the majority of our revenue from the natural gas gathering services that we provide to our natural gas producer customers. We also generate revenue from our marketing of natural gas and natural gas liquids ("NGLs"). We realize revenues by receiving fees from our producer customers or by selling the residue natural gas and NGLs.

We recognize revenue earned from gathering services in gathering services and other fees revenue. We also earn revenue from the sale of physical natural gas purchased from our customers under percentage-of-proceeds arrangements. These revenues are recognized in natural gas, NGLs and condensate sales and other with corresponding expense recognition in cost of natural gas and NGLs. We sell the natural gas that we retain from our DFW Midstream customers to offset the power expenses of the electric-driven compression on the DFW Midstream system. We also sell condensate retained from our gathering services at Grand River Gathering. Revenues from the retainage of natural gas and condensate are recognized in natural gas, NGLs and condensate sales and other; the associated expense is included in operation and maintenance expense. Certain customers reimburse us for costs we incur on their behalf. We record costs incurred and reimbursed by our customers on a gross basis.

We recognize revenue when all of the following criteria are met: (i) persuasive evidence of an exchange arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the price is fixed or determinable, and (iv) collectability is reasonably assured.

We obtain access to natural gas and provide services principally under contracts that contain one or both of the following arrangements:

•

Fee-based arrangements. Under fee-based arrangements, we receive a fee or fees for one or more of the following services: natural gas gathering, compressing, and treating. Fee-based arrangements include natural gas purchase arrangements pursuant to which we purchase natural gas at the wellhead, or other receipt points, at a settled price at the delivery point less a specified amount, generally the same as the fees we would otherwise charge for gathering of natural gas from the wellhead location to the delivery point. The margins earned are directly related to the volume of natural gas that flows through the system.

•

Percent-of-proceeds arrangements. Under percent-of-proceeds arrangements, we generally purchase natural gas from producers at the wellhead, or other receipt points, gather the wellhead natural gas through our gathering system, treat the natural gas, and sell the natural gas to a third party for processing. We then remit to our producers an agreed-upon percentage of the actual proceeds received from sales of the residue natural gas and NGLs. Certain of these arrangements may also result in returning all or a portion of the residue natural gas and/or the NGLs to the producer, in lieu of returning sales proceeds.

Many of our natural gas gathering agreements provide for a monthly or annual minimum volume commitment ("MVC") from certain of our customers. Under these monthly or annual MVCs, our customers agree to ship a minimum volume of natural gas on our gathering systems or to pay a minimum monetary amount over certain periods during the term of the MVC. A customer must make a shortfall payment to us at the end of the contract month or year, as applicable, if its actual throughput volumes are less than its MVC for that month or year. Certain customers are entitled to utilize shortfall payments to offset gathering fees in one or more subsequent periods to the extent that such customer's throughput volumes in subsequent periods exceed its MVC for that period. These contract provisions range from 12 months to eight years.

We record customer billings for obligations under their MVCs as deferred revenue when the customer has the right to utilize shortfall payments to offset gathering fees in subsequent periods. We recognize deferred revenue under these arrangements in revenue once all contingencies or potential performance obligations associated with the related volumes have either (i) been satisfied through the gathering of future excess volumes of natural gas, or (ii) expired (or lapsed) through the passage of time pursuant to the terms of the applicable natural gas gathering agreement. We classify deferred revenue as current for arrangements where the expiration of a customer's right to utilize shortfall payments is twelve months or less. A rollforward of current and noncurrent deferred revenue follows.



	Current		Noncurrent
	(In thousands)
Deferred revenue, January 1, 2012	$	—	$	1,770
Additions	865		9,129
Deferred revenue, December 31, 2012	865		10,899
Additions (1)	1,555		18,784
Less: revenue recognized due to expiration	865		—
Deferred revenue, December 31, 2013	$	1,555	$	29,683

__________

(1) Noncurrent includes amounts recognized in connection with the Bison Drop Down.

As of December 31, 2013, we have $1.1 million included in accounts receivable for shortfall payments related to MVC arrangements which can be utilized to offset gathering fees in subsequent periods. Current and noncurrent deferred revenue at December 31, 2013 includes amounts that provide the customer the ability to offset gathering fees in the next one month to eight years to the extent that the customer's throughput volumes exceed its MVC.

Unit-Based Compensation. For awards of unit-based compensation, we determine a grant date fair value and recognize the related compensation expense, in the statement of operations over the vesting period of the respective awards. See Note 8 for additional information.

Income Taxes. We are not subject to federal and state income taxes, except as noted below, because we are structured as a partnership. As a result, our unitholders or members are individually responsible for paying federal and state income taxes on their share of our taxable income.

In general, legal entities that are chartered, organized or conducting business in the state of Texas are subject to the Revised Texas Franchise Tax (the "Texas Margin Tax"). The Texas Margin Tax has the characteristics of an income tax because it is determined by applying a tax rate to a tax base that considers both revenues and expenses. Our financial statements reflect provisions for these tax obligations.

Earnings Per Unit ("EPU"). We present earnings per limited partner unit data only for periods subsequent to the closing of SMLP’s IPO in October 2012. EPU for periods ended prior to the IPO have not been presented because Summit Investments' members held membership interests and not units.

We determine EPU by dividing the net income that is attributed, in accordance with the net income and loss allocation provisions of the partnership agreement, to the common and subordinated unitholders under the two-class method, after deducting the general partner's 2% interest in net income and any payments to the general partner in connection with their incentive distribution rights ("IDRs"), by the weighted-average number of common and subordinated units outstanding during the year ended December 31, 2013 and the period from October 1, 2012 to December 31, 2012. Diluted earnings per limited partner unit reflects the potential dilution that could occur if securities or other agreements to issue common units, such as unit-based compensation, were exercised, settled or converted into common units. When it is determined that potential common units resulting from an award subject to performance or market conditions should be included in the diluted earnings per limited partner unit calculation, the impact is reflected by applying the treasury stock method.

Comprehensive Income. Comprehensive income is the same as net income for all periods presented.

Environmental Matters. We are subject to various federal, state and local laws and regulations relating to the protection of the environment. Although we believe that we are in material compliance with applicable environmental regulations, the risk of costs and liabilities are inherent in pipeline ownership and operation. Liabilities for loss contingencies, including environmental remediation costs, arising from claims, assessments, litigation, fines, and penalties and other sources are charged to expense when it is probable that a liability has been incurred and the amount of the assessment and/or remediation can be reasonably estimated. There are no such liabilities reflected in the accompanying financial statements at December 31, 2013 or 2012. However, we can provide no assurances that significant costs and liabilities will not be incurred by the Partnership in the future. We are currently not aware of any material contingent liabilities that exist with respect to environmental matters.

Recent Accounting Pronouncements. Accounting standard setters frequently issue new or revised accounting rules. We review new pronouncements to determine the impact, if any, on our financial statements. There are currently no recent pronouncements that have been issued that we believe will materially affect our financial statements.

PROPERTY, PLANT, AND EQUIPMENT, NET

12 Months Ended

Dec. 31, 2013

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT, AND EQUIPMENT, NET

Details on property, plant, and equipment, net were as follows:



	Useful lives (In years)	December 31,
	Useful lives (In years)	2013			2012
	(Dollars in thousands)
Gas gathering systems	30	$	634,177		$	427,449
Compressor stations and compression equipment	30	351,560			237,618
Construction in progress	n/a	51,023			45,919
Other	4-15	7,451			4,524
Total		1,044,211			715,510
Accumulated depreciation		(63,870		)	(33,517		)
Property, plant, and equipment, net		$	980,341		$	681,993

The increase in property, plant, and equipment primarily reflects the recognition of gas gathering system fixed assets acquired in connection with the Bison Drop Down and Mountaineer Acquisition. See Note 13 for additional information.

Construction in progress is depreciated consistent with its applicable asset class once it is placed in service. Depreciation expense related to property, plant, and equipment and capitalized interest were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Depreciation expense	$	30,353	$	21,337	$	8,595
Capitalized interest	4,209		2,784		3,362

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL

12 Months Ended

Dec. 31, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

IDENTIFIABLE INTANGIBLE ASSETS AND NONCURRENT LIABILITY

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL

Identifiable Intangible Assets and Noncurrent Liability. Identifiable intangible assets and the noncurrent liability, which are subject to amortization, were as follows:



	December 31, 2013
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(6,315	)	$	17,880
Contract intangibles	12.5	426,464		(43,158		)	383,306
Rights-of-way	28.3	56,487		(4,679		)	51,808
Total amortizable intangible assets		$	507,146	$	(54,152	)	$	452,994

Unfavorable gas gathering contract	10.0	$	10,962	$	(4,588	)	$	6,374



	December 31, 2012
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(4,237	)	$	19,958
Contract intangibles	12.4	244,100		(14,504		)	229,596
Rights-of-way	28.3	38,848		(2,862		)	35,986
Total amortizable intangible assets		$	307,143	$	(21,603	)	$	285,540

Unfavorable gas gathering contract	10.0	$	10,962	$	(3,542	)	$	7,420

The increase in total amortizable intangible assets primarily reflects the recognition of gas gathering contracts and rights-of-way acquired in connection with the Bison Drop Down and the Mountaineer Acquisition. See Note 13 for additional information.

We recognized amortization expense as follows:



	Year ended December 31,
	2013			2012			2011
	(In thousands)
Amortization expense – favorable gas gathering contracts	$	2,078		$	1,715		$	1,718
Amortization expense – contract intangibles	28,654			12,642			1,862
Amortization expense – rights-of-way	1,817			1,321			908
Amortization expense – unfavorable gas gathering contract	(1,046		)	(1,524		)	(1,410		)

The estimated aggregate annual amortization of intangible assets and noncurrent liability expected to be recognized as of December 31, 2013 for each of the five succeeding fiscal years follows.



	Assets		Liabilities
	(In thousands)
2014	$	37,893	$	1,549
2015	40,912		1,650
2016	41,167		1,571
2017	39,903		1,604
2018	39,448		—

Goodwill. We recognized goodwill of $45.5 million in connection with the acquisition of Grand River Gathering in 2011 and allocated it to the Grand River Gathering reporting unit. We recognized goodwill of $54.2 million in connection with the Bison Drop Down in June 2013 and allocated it to the Bison Midstream reporting unit. The goodwill attributed to Bison Midstream represents its allocation of the goodwill that Summit Investments recognized in connection with its acquisition of BTE assets in February 2013. We preliminarily recognized goodwill of $18.1 million in connection with the Mountaineer Acquisition in June 2013 and allocated it to the Mountaineer Midstream reporting unit. Prior to the issuance of the financial statements, we received the remaining information needed to finalize accounting for the Mountaineer Acquisition and recognized an adjustment, which reduced the preliminary goodwill recognition by $1.9 million. See Notes 1 and 13 for additional information. A rollforward of the consolidated balance of goodwill follows (in thousands).



Goodwill, December 31, 2012 and 2011	$	45,478
Goodwill recognized in connection with the Bison Drop Down	54,199
Goodwill preliminarily recognized in connection with the Mountaineer Acquisition	18,089
Goodwill adjustment recognized in connection with finalizing accounting for the Mountaineer Acquisition and other	(1,878		)
Goodwill, December 31, 2013	$	115,888

We evaluate goodwill for impairment annually on September 30. We also evaluate goodwill whenever events or circumstances indicate that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. We performed our annual goodwill impairment testing as of September 30, 2013 using a combination of the income and market approaches and determined that the fair value of each of these three reporting units exceeded its carrying value resulting in no goodwill impairment. There have been no impairments of goodwill and there is no goodwill associated with the DFW Midstream reporting unit.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

LONG-TERM DEBT

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

LONG-TERM DEBT

Long-term debt consisted of the following:



	December 31,
	2013		2012
	(In thousands)
Variable rate senior secured revolving credit facility (2.42% at December 31, 2013 and 2.98% at December 31, 2012) due November 2018	$	286,000	$	199,230
7.50% Senior unsecured notes due July 2021	300,000		—
Total long-term debt	$	586,000	$	199,230

Revolving Credit Facility. We have a senior secured revolving credit facility. In June 2013, we exercised the revolving credit facility's $50.0 million accordion provision and increased the total commitments thereunder from $550.0 million to $600.0 million. We also borrowed $200.0 million in connection with the Bison Drop Down and $110.0 million in connection with the Mountaineer Acquisition. See Notes 1, 6 and 12 for additional information. Also in June 2013, we used the proceeds from our senior notes offering to repay $294.2 million of our revolving credit facility. In November 2013, we closed on an amendment and restatement of the revolving credit facility which: (i) increased the borrowing capacity to $700.0 million, (ii) extended the maturity to November 2018, (iii) included a $200.0 million accordion feature, (iv) reduced the leverage-based pricing grid by 0.75% to a new range of 1.75% to 2.75% for LIBOR borrowings, (v) changed the commitment fee to a leverage-based range of 0.30% to 0.50%, and (vi) added Summit Midstream Finance Corp. ("Finance Corp.") as a subsidiary guarantor.

The revolving credit facility is secured by the membership interests of Summit Holdings and those of its subsidiaries. Substantially all of Summit Holdings' and its subsidiaries' assets are pledged as collateral under the revolving credit facility. The revolving credit facility, and Summit Holdings' obligations, are guaranteed by SMLP and each of its subsidiaries and allows for revolving loans, letters of credit and swingline loans.

Borrowings under the revolving credit facility bear interest at the London Interbank Offered Rate ("LIBOR") plus an applicable margin or a base rate, as defined in the credit agreement. At December 31, 2013, the applicable margin under LIBOR borrowings was 2.25%, the interest rate was 2.42% and the unused portion of the revolving credit facility totaled $414.0 million (subject to a commitment fee of 0.375%).

The revolving credit agreement contains affirmative and negative covenants customary for credit facilities of its size and nature that, among other things, limit or restrict the ability to: (i) incur additional debt; (ii) make investments; (iii) engage in certain mergers, consolidations, acquisitions or sales of assets; (iv) enter into swap agreements and power purchase agreements; (v) enter into leases that would cumulatively obligate payments in excess of $30.0 million over any 12-month period; and (vi) prohibits the payment of distributions by Summit Holdings if a default then exists or would result therefrom, and otherwise limits the amount of distributions Summit Holdings can make. In addition, the revolving credit facility requires Summit Holdings to maintain a ratio of consolidated trailing 12-month earnings before interest, income taxes, depreciation and amortization ("EBITDA") to net interest expense of not less than 2.5 to 1.0 (as defined in the credit agreement) and a ratio of total net indebtedness to consolidated trailing 12-month EBITDA of not more than 5.0 to 1.0, or not more than 5.5 to 1.0 for up to 270 days following certain acquisitions (as defined in the credit agreement).

As of December 31, 2013, we were in compliance with the covenants in the revolving credit facility. There were no defaults or events of default during the year ended December 31, 2013.

Senior Notes. On June 17, 2013, Summit Holdings and its 100% owned finance subsidiary, Finance Corp. (together with Summit Holdings, the "Co-Issuers"), issued $300.0 million of 7.50% senior unsecured notes maturing July 1, 2021 (the "senior notes"). The senior notes were sold within the United States only to qualified institutional buyers in reliance on Rule 144A under the Securities Act of 1933, as amended (the "Securities Act"), and outside the United States only to non-U.S. persons in reliance on Regulation S under the Securities Act. The senior notes have not been registered under the Securities Act or any state securities laws, and, unless so registered, may not be offered or sold in the United States except pursuant to an exemption from, or in a transaction not subject to, the registration requirements of the Securities Act and applicable state securities laws.

We will pay interest on the senior notes semi-annually in cash in arrears on January 1 and July 1 of each year, commencing January 1, 2014. The senior notes are senior, unsecured obligations and rank equally in right of payment with all of our existing and future senior obligations. The senior notes are effectively subordinated in right of payment to all of our secured indebtedness, to the extent of the collateral securing such indebtedness. We used the proceeds from the issuance of the senior notes to repay a portion of the balance outstanding under our revolving credit facility. Debt issuance costs of $7.3 million, recognized in other noncurrent assets, are being amortized over the life of the senior notes.

SMLP and all of its subsidiaries other than the Co-Issuers (the "Guarantors") have fully and unconditionally and jointly and severally guaranteed the senior notes. SMLP has no independent assets or operations. Summit Holdings has no assets or operations other than its ownership of its wholly owned subsidiaries and activities associated with its borrowings under the revolving credit facility and the senior notes. Finance Corp. has no independent assets or operations and was formed for the sole purpose of being a co-issuer of certain of Summit Holdings' indebtedness, including the senior notes. There are no significant restrictions on the ability of SMLP or Summit Holdings to obtain funds from its subsidiaries by dividend or loan.

In connection with the associated registration rights agreement, the Co-Issuers and the Guarantors agreed to file a registration statement with the SEC pursuant to which the Co-Issuers will either offer to exchange the senior notes and the guarantees for registered notes and guarantees with substantially identical terms or, in certain circumstances, register the resale of the senior notes and their guarantees (the "Exchange Offer"). In January 2014, we filed a registration statement on Form S-4 to offer to exchange all of the unregistered senior notes and guarantees for registered notes and guarantees with substantially identical terms. The terms of the registered senior notes are substantially identical to the terms of the unregistered senior notes, except that the transfer restrictions, registration rights and provisions for additional interest relating to the unregistered senior notes do not apply to the registered senior notes. On March 7, 2014, the SEC declared our registration statement effective and we began the notice process to properly effect the exchange. The period during which exchanges can occur will end on April 7, 2014. If a holder of the unregistered senior notes does not exchange them for the registered senior notes, such holder will no longer be able to require us to register their private note holdings under the Securities Act, except in limited circumstances provided under the registration rights agreement.

If the Exchange Offer is not completed (or, if required, the shelf registration statement is not declared effective or does not automatically become effective) on or before the 365th day following the date of issuance of the senior notes (the ‘‘Exchange Completion Deadline’’), the Co-Issuers will be required to pay additional interest in an amount equal to 0.25% per annum of the principal amount of senior notes with respect to the first 90-day period following the Exchange Completion Deadline. The amount of the additional interest will increase by an additional 0.25% per annum with respect to each subsequent 90-day period, up to a maximum amount of additional interest of 1.0% per annum of the principal amount of senior notes outstanding until the Exchange Offer is completed or the shelf registration statement is declared effective (or becomes automatically effective). All accrued additional interest will be paid by the Co-Issuers and the Guarantors on the next scheduled interest payment date in the same manner as other interest is paid on the senior notes. Following the time that the senior notes are registered, the accrual of additional interest will cease.

At any time prior to July 1, 2016, the Co-Issuers may redeem up to 35% of the aggregate principal amount of the senior notes at a redemption price of 107.500% of the principal amount of the senior notes, plus accrued and unpaid interest, if any, to the redemption date, with an amount not greater than the net cash proceeds of certain equity offerings. On and after July 1, 2016, the Co-Issuers may redeem all or part of the senior notes at a redemption price of 105.625% (with the redemption premium declining ratably each year to 100.000% on July 1, 2019), plus accrued and unpaid interest, if any.

The indenture restricts SMLP’s and the Co-Issuers’ ability and the ability of certain of their subsidiaries to: (i) incur additional debt or issue preferred stock; (ii) make distributions, repurchase equity or redeem subordinated debt; (iii) make payments on subordinated indebtedness; (iv) create liens or other encumbrances; (v) make investments, loans or other guarantees; (vi) sell or otherwise dispose of a portion of their assets; (vii) engage in transactions with affiliates; and (viii) make acquisitions or merge or consolidate with another entity. These covenants are subject to a number of important exceptions and qualifications. At any time when the senior notes are rated investment grade by each of Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services and no default or event of default under the indenture has occurred and is continuing, many of these covenants will terminate.

The indenture provides that each of the following is an event of default: (i) default for 30 days in the payment when due of interest on the senior notes; (ii) default in the payment when due of the principal of, or premium, if any, on the senior notes; (iii) failure by the Co-Issuers or SMLP to comply with certain covenants relating to merger, consolidation, sale of assets, change of control or asset sales; (iv) failure by SMLP for 180 days after notice to comply with certain covenants relating to the filing of reports with the SEC; (v) failure by the Co-Issuers or SMLP for 30 days after notice to comply with any of the other agreements in the indenture; (vi) specified defaults under any mortgage, indenture or instrument under which there may be issued or by which there may be secured or evidenced any indebtedness for money borrowed by SMLP or any of its restricted subsidiaries (or the payment of which is guaranteed by SMLP or any of its restricted subsidiaries); (vii) failure by SMLP or any of its restricted subsidiaries to pay certain final judgments aggregating in excess of $20.0 million; (viii) except as permitted by the indenture, any guarantee of the senior notes shall cease for any reason to be in full force and effect or any guarantor, or any person acting on behalf of any guarantor, shall deny or disaffirm its obligations under its guarantee of the senior notes; and (ix) certain events of bankruptcy, insolvency or reorganization described in the indenture. In the case of an event of default as described in the foregoing clause (ix), all outstanding senior notes will become due and payable immediately without further action or notice. If any other event of default occurs and is continuing, the trustee or the holders of at least 25% in principal amount of the then outstanding senior notes may declare all the senior notes to be due and payable immediately.

As of December 31, 2013, we were in compliance with the covenants for the senior notes. There were no defaults or events of default during the period from issuance through December 31, 2013.

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS

12 Months Ended

Dec. 31, 2013

Equity [Abstract]

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS

Partners' Capital

SMLP was formed in May 2012. Prior to the closing of its IPO on October 3, 2012, SMLP had no outstanding common or subordinated units or operations. A rollforward of the number of common limited partner, subordinated limited partner and general partner units follows.



	Common	Subordinated	General partner	Total
Units, January 1, 2012	—	—	—	—
Units issued to the public in connection with the IPO	14,380,000	—	—	14,380,000
Units issued to affiliates in connection with the IPO	10,029,850	24,409,850	996,320	35,436,020
Units issued	2,577	—	—	2,577
Units, December 31, 2012	24,412,427	24,409,850	996,320	49,818,597
Units issued to affiliates in connection with the Bison Drop Down	1,553,849	—	31,711	1,585,560
Units issued to affiliates in connection with the Mountaineer Acquisition	3,107,698	—	63,422	3,171,120
Units issued	5,892	—	—	5,892
Units, December 31, 2013	29,079,866	24,409,850	1,091,453	54,581,169

Bison Drop Down. On June 4, 2013, SMLP acquired Bison Midstream from SMP Holdings. SMP Holdings contributed 100% of the membership interests in Bison Midstream to SMLP, which concurrently contributed the membership interests to Summit Holdings. In exchange for its $305.4 million net investment in Bison Midstream, SMLP paid SMP Holdings and the general partner total cash and unit consideration of $248.9 million. As a result of the contribution of net assets in excess of consideration, SMLP recognized a capital contribution from SMP Holdings. The details of total cash and unit consideration as well as the calculation of the capital contribution and its allocation to partners' capital follow (dollars in thousands).



SMP Holdings' net investment in Bison Midstream			$	305,449
Aggregate cash paid to SMP Holdings	$	200,000
Issuance of 1,553,849 SMLP common units to SMP Holdings	47,936
Issuance of 31,711 SMLP general partner units to the general partner	978
Total consideration			248,914
SMP Holdings' contribution of net assets in excess of consideration			$	56,535

Allocation of capital contribution:
General partner interest	$	1,131
Common limited partner interest	28,558
Subordinated limited partner interest	26,846
Partners' capital allocation			$	56,535

The number of units issued to SMP Holdings and the general partner in connection with the Bison Drop Down was calculated based on an assumed equity issuance of $50.0 million and the five-day volume-weighted-average price as of June 3, 2013 of $31.53 per unit. The units were then valued as of June 4, 2013 (the date of closing) using the June 4, 2013 closing price of SMLP's units of $30.85.

The general partner interest allocation was calculated based on a 2% general partner interest in the contribution of assets in excess of consideration given by SMLP to SMP Holdings. Common and subordinated limited partner interests allocations were calculated as their respective percentages of total limited partner capital applied to the balance of the contribution by SMP Holdings after giving effect to the general partner allocation. See Notes 1, 5 and 13 for additional information.

Mountaineer Acquisition. On June 4, 2013, SMLP executed definitive agreements with MarkWest to acquire the Mountaineer Midstream system. On June 21, 2013, prior to closing the Mountaineer Acquisition and in accordance with the definitive agreements with MarkWest (the "MarkWest Agreement"), Mountaineer Midstream acquired all of the Mountaineer Gathering system assets. The total acquisition purchase price of $210.0 million was funded with $110.0 million of borrowings under SMLP’s revolving credit facility and the issuance of $100.0 million of SMLP common units and general partner interests to SMP Holdings and the general partner for cash. The allocation and valuation of units issued to SMP Holdings and the general partner to partially fund the Mountaineer Acquisition follow (dollars in thousands).



Issuance of 3,107,698 SMLP common units to SMP Holdings	$	98,000
Issuance of 63,422 SMLP general partner units to the general partner	2,000
Issuance of units in connection with the Mountaineer Acquisition	$	100,000

Pursuant to a unit purchase agreement, the number of units issued to SMP Holdings and the general partner in connection with the Mountaineer Acquisition was calculated based on an assumed equity issuance of $100.0 million and the five-day volume-weighted-average price as of June 3, 2013 of $31.53 per unit. See Notes 1, 5 and 13 for additional information.

Subordination. The principal difference between our common units and subordinated units is that in any quarter during the subordination period, holders of the subordinated units are not entitled to receive any distribution of available cash until the common units have received the minimum quarterly distribution plus any arrearages in the payment of the minimum quarterly distribution from prior quarters. Subordinated units will not accrue arrearages for unpaid quarterly distributions or quarterly distributions less than the minimum quarterly distribution. If we do not pay the minimum quarterly distribution on our common units, our common unitholders will not be entitled to receive such payments in the future except during the subordination period. To the extent we have available cash in any future quarter during the subordination period in excess of the amount necessary to pay the minimum quarterly distribution to holders of our common units, we will use this excess available cash to pay any distribution arrearages related to prior quarters before any cash distribution is made to holders of subordinated units. When the subordination period ends, all subordinated units will convert into common units on a one-for-one basis, and thereafter no common units will be entitled to arrearages.

The subordination period will end on the first business day after we have earned and paid at least (1) $1.60 (the minimum quarterly distribution on an annualized basis) on each outstanding common unit and subordinated unit and the corresponding distribution on the general partner's 2.0% interest for each of three consecutive, non-overlapping four-quarter periods ending on or after December 31, 2015 or (2) $2.40 (150.0% of the annualized minimum quarterly distribution) on each outstanding common unit and subordinated unit and the corresponding distributions on the general partner's 2.0% interest and the related distribution on the incentive distribution rights for the four-quarter period immediately preceding that date, in each case provided there are no arrearages on the common units at that time.

Cash Distribution Policy

Our partnership agreement requires that we distribute all of our available cash (as defined below) within 45 days after the end of each quarter to unitholders of record on the applicable record date. Our policy is to distribute to our unitholders an amount of cash each quarter that is equal to or greater than the minimum quarterly distribution stated in our partnership agreement.

Minimum Quarterly Distribution. Our partnership agreement generally requires that we make a minimum quarterly distribution to the holders of our common units and subordinated units of $0.40 per unit, or $1.60 on an annualized basis, to the extent we have sufficient cash from our operations after the establishment of cash reserves and the payment of costs and expenses, including reimbursements of expenses to our general partner. The amount of distributions paid under our policy and the decision to make any distribution is determined by our general partner, taking into consideration the terms of our partnership agreement.

Definition of Available Cash. Available cash generally means, for any quarter, all cash on hand at the end of that quarter:


•	less the amount of cash reserves established by our general partner at the date of determination of available cash for that quarter to:


•	provide for the proper conduct of our business (including reserves for our future capital expenditures and anticipated future debt service requirements);


•	comply with applicable law, any of our debt instruments or other agreements; or

•

provide funds for distributions to our unitholders and to our general partner for any one or more of the next four quarters (provided that our general partner may not establish cash reserves for distributions unless it determines that the establishment of reserves will not prevent us from distributing the minimum quarterly distribution on all common units and any cumulative arrearages on such common units for the current quarter);


•	plus, if our general partner so determines, all or any portion of the cash on hand on the date of determination of available cash for the quarter resulting from working capital borrowings made subsequent to the end of such quarter.

General Partner Interest and Incentive Distribution Rights. Our general partner is entitled to 2.0% of all distributions that we make prior to our liquidation. Our general partner has the right, but not the obligation, to contribute a proportionate amount of capital to us to maintain its current general partner interest. Our general partner's initial 2.0% interest in our distributions will be reduced if we issue additional units in the future and our general partner does not contribute a proportionate amount of capital to us to maintain its 2.0% general partner interest.

Our general partner also currently holds incentive distribution rights that entitle it to receive increasing percentage allocations, up to a maximum of 50.0% (as set forth in the chart below), of the cash we distribute from operating surplus in excess of $0.46 per unit per quarter. The maximum distribution of 50.0% includes distributions paid to our general partner on its 2.0% general partner interest and assumes that our general partner maintains its general partner interest at 2.0%. The maximum distribution of 50.0% does not include any distributions that our general partner may receive on any common or subordinated units that it owns.

Percentage Allocations of Available Cash. The following table illustrates the percentage allocations of available cash between the unitholders and our general partner based on the specified target distribution levels. The amounts set forth in the column Marginal Percentage Interest in Distributions are the percentage interests of our general partner and the unitholders in any available cash we distribute up to and including the corresponding amount in the column Total Quarterly Distribution Per Unit Target Amount. The percentage interests shown for our unitholders and our general partner for the minimum quarterly distribution are also applicable to quarterly distribution amounts that are less than the minimum quarterly distribution. The percentage interests set forth below for our general partner include its 2.0% general partner interest and assume that our general partner has contributed any additional capital necessary to maintain its 2.0% general partner interest, our general partner has not transferred its incentive distribution rights and that there are no arrearages on common units.



	Total quarterly distribution per unit target amount	Marginal percentage interest in distributions
	Total quarterly distribution per unit target amount	Unitholders	General partner
Minimum quarterly distribution	$0.40	98.0%	2.0%
First target distribution	$0.40 up to $0.46	98.0%	2.0%
Second target distribution	above $0.46 up to $0.50	85.0%	15.0%
Third target distribution	above $0.50 up to $0.60	75.0%	25.0%
Thereafter	above $0.60	50.0%	50.0%

Details of cash distributions declared follow.



Attributable to the quarter ended	Payment date	Per-unit distribution		Cash paid (or payable) to common unitholders		Cash paid (or payable) to subordinated unitholders		Cash paid (or payable) to general partner ⁽¹⁾		Total distribution
		(Dollars in thousands, except per-unit amounts)
December 31, 2012	February 14, 2013	$	0.4100	$	10,009	$	10,008	$	408	$	20,425
March 31, 2013	May 15, 2013	0.4200		10,253		10,252		418		20,923
June 30, 2013	August 14, 2013	0.4350		12,647		10,618		475		23,740
September 30, 2013	November 14, 2013	0.4600		13,377		11,229		502		25,108
December 31, 2013	February 14, 2014	0.4800		13,958		11,717		691		26,366

__________

(1) Distributions attributable to the quarter ended December 31, 2013 include payments associated with the general partner's IDRs, which totaled $163,000. Our general partner was not entitled to receive incentive distributions for periods prior to the fourth quarter of 2013 based on the amount of the distributions declared per common and subordinated unit.

Membership Interests

Energy Capital Partners and GE Energy Financial Services hold membership interests in Summit Investments. Such membership interests give them the right to participate in distributions and to exercise the other rights or privileges available to each entity under Summit Investments' Amended and Restated Limited Liability Operating Agreement (the "Summit LLC Agreement"). In addition, certain members of Summit Investments’ management hold ownership interests in the form of Class B membership interests (the "SMP Net Profits Interests") through their ownership in Summit Midstream Management, LLC.

In accordance with the Summit LLC Agreement, capital accounts are maintained for Summit Investments’ members. The capital account provisions of the Summit LLC Agreement incorporate principles established for U.S. federal income tax purposes and as such are not comparable to the equity accounts reflected under GAAP in our consolidated financial statements.

The Summit LLC Agreement sets forth the calculation to be used in determining the amount and priority of cash distributions that its membership interest holders will receive. Capital contributions required under the Summit LLC Agreement are in proportion to the members' respective percentage ownership interests. The Summit LLC Agreement also contains provisions for the allocation of net earnings and losses to members. For purposes of maintaining partner capital accounts, the Summit LLC Agreement specifies that items of income and loss shall be allocated among the partners in accordance with their respective percentage interests.

In April 2013, we repurchased the outstanding net profits interests in DFW Midstream. See Note 8 for additional information.

EARNINGS PER UNIT

12 Months Ended

Dec. 31, 2013

Earnings Per Share [Abstract]

EARNINGS PER UNIT

The following table presents details on EPU.



	Year ended December 31,
	2013		2012 ⁽¹⁾
	(Dollars in thousands, except per-unit amounts)
Net income	$	43,636	$	41,726
Less: net income attributable to the pre-IPO period	—		24,112
Less: net income attributable to SMP Holdings	52		—
Net income attributable to SMLP	43,584		17,614
Less: net income attributable to general partner, including IDRs	1,035		352
Net income attributable to limited partners	$	42,549	$	17,262

Numerator for basic and diluted EPU:
Allocation of net income among limited partner interests:
Net income attributable to common units	$	23,227	$	8,632
Net income attributable to subordinated units	19,322		8,630
Net income attributable to limited partners	$	42,549	$	17,262

Denominator for basic and diluted EPU:
Weighted-average common units outstanding – basic	26,951,346		24,412,427
Less: effect of non-vested phantom units and non-vested restricted units	150,133		131,558
Weighted-average common units outstanding – diluted	27,101,479		24,543,985

Weighted-average subordinated units outstanding – basic and diluted	24,409,850		24,409,850

Net income per limited partner unit:
Common unit – basic	$	0.86	$	0.35
Common unit – diluted	$	0.86	$	0.35
Subordinated unit – basic and diluted	$	0.79	$	0.35

__________

(1) Calculated for the period from October 1, 2012 to December 31, 2012

Our general partner was not entitled to receive incentive distributions for periods prior to the fourth quarter of 2013 based on the amount of the distributions declared per common and subordinated unit. There were no units excluded from diluted earnings per unit as we do not have any anti-dilutive units for the year ended December 31, 2013 or for the period from October 1, 2012 to December 31, 2012. See Notes 6 and 8 for additional information.

UNIT-BASED COMPENSATION

12 Months Ended

Dec. 31, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

UNIT-BASED COMPENSATION

Long-Term Incentive Plan. The Long-Term Incentive Plan (the "LTIP") provides for equity awards to eligible officers, employees, consultants and directors of our general partner and its affiliates, thereby linking the recipients' compensation directly to SMLP’s performance. The LTIP is administered by our general partner's board of directors, though such administration function may be delegated to a committee appointed by the board. A total of 5.0 million common units was reserved for issuance pursuant to and in accordance with the LTIP. As of December 31, 2013, approximately 4.7 million common units remained available for future issuance.

The LTIP provides for the granting, from time to time, of unit-based awards, including common units, restricted units, phantom units, unit options, unit appreciation rights, distribution equivalent rights, profits interest units and other unit-based awards. Grants are made at the discretion of the board of directors or compensation committee of our general partner. The administrator of the LTIP may make grants under the LTIP that contain such terms, consistent with the LTIP, as the administrator may determine are appropriate, including vesting conditions. The administrator of the LTIP may, in its discretion, base vesting on the grantee's completion of a period of service or upon the achievement of specified financial objectives or other criteria or upon a change of control (as defined in the LTIP) or as otherwise described in an award agreement. Termination of employment prior to vesting will result in forfeiture of the awards, except in limited circumstances as described in the plan documents. Units that are canceled or forfeited will be available for delivery pursuant to other awards.

The following table presents phantom and restricted unit activity:



	Units		Weighted-average grant date fair value
Nonvested phantom and restricted units, January 1, 2012	—		$	—
Phantom units granted	125,000		$	20.00
Restricted units granted	6,558		$	20.23
Nonvested phantom and restricted units, December 31, 2012	131,558		$	20.00
Phantom units granted	155,330		$	26.33
Restricted units granted	835		$	27.50
Phantom units forfeited	(4,041	)	$	25.99
Nonvested phantom and restricted units, December 31, 2013	283,682		$	23.41

A phantom unit is a notional unit that entitles the grantee to receive a common unit upon the vesting of the phantom unit or on a deferred basis upon specified future dates or events or, in the discretion of the administrator, cash equal to the fair market value of a common unit. Distribution equivalent rights for each phantom unit provide for a lump sum cash amount equal to the accrued distributions from the grant date to be paid in cash upon the vesting date. The phantom units granted in connection with the IPO vest on the third anniversary of the IPO. All other phantom unit grants vest ratably over a three-year period. Grant date fair value is determined based on the closing price our our common units on the date of grant multiplied by the number of phantom units awarded to the grantee. Upon vesting, phantom unit awards may be settled in cash and/or common units, at the discretion of the board of directors. The restricted units granted in 2012 and 2013 maintained the vesting provisions of the share-based compensation awards they replaced, each of which had an original vesting period of four years. See "—DFW Net Profits Interests" for additional information.

Upon vesting, management intends to settle all phantom unit awards with common units. As of December 31, 2013, the unrecognized unit-based compensation related to the LTIP was $3.6 million. Incremental unit-based compensation will be recorded over the remaining vesting period of 2.67 years. Due to the limited and immaterial forfeiture history associated with the grants under the LTIP, no forfeitures were assumed in the determination of estimated compensation expense.

Unit-based compensation recognized in general and administrative expense related to awards under the LTIP was as follows:



	Year ended December 31, 2013
	2013		2012		2011
	(In thousands)
SMLP unit-based compensation	$	2,999	$	269	$	—

DFW Net Profits Interests. In connection with the formation of DFW Midstream in 2009, up to 5% of DFW Midstream's total membership interests were authorized for issuance as Class B membership interests (the "DFW Net Profits Interests"). Beginning in October 2012 and continuing into April 2013, we entered into a series of repurchases with the remaining seven holders of the then-outstanding DFW Net Profits Interests whereby we exchanged $12.2 million for their vested DFW Net Profits Interests and 7,393 SMLP restricted units for their unvested DFW Net Profits Interests. The repurchase prices were determined by valuing the vested and unvested net profits interests in relation to the enterprise value of DFW Midstream and represented fair value at the dates of repurchase. Upon the conclusion of these repurchase transactions, there were no remaining or outstanding DFW Net Profits Interests.

The DFW Net Profits Interests participated in distributions upon time vesting and the achievement of certain distribution targets to Class A members or higher priority vested DFW Net Profits Interests and were accounted for as compensatory awards. In addition to the net profits interests granted in 2009, additional DFW Net Profits Interests were granted on April 1, 2010 and July 28, 2010. Each grant vested ratably over four years and provided for accelerated vesting in certain limited circumstances, including a qualifying termination following a change in control (as defined in the underlying award agreement and LLC Agreement).

We determined the fair value of the DFW Net Profits Interests as of the respective grant dates for the grants made prior to that date with assistance from a third-party valuation expert in 2011. As such, the 2009 and 2010 awards were valued retrospectively. The DFW Net Profits Interests were valued utilizing an option pricing method, which modeled the Class A and Class B membership interests as call options on the underlying equity value of DFW Midstream and considered the rights and preferences of each class of equity in order to allocate a fair value to each class.

A significant input of the option pricing method was the enterprise value of DFW Midstream. We estimated the enterprise value utilizing a combination of the income and market approaches. The income approach utilized the discounted cash flow method, whereby we applied a discount rate to estimated future cash flows of DFW Midstream. Key inputs included forecasted gathering volumes, revenues and costs; unlevered equity betas of the DFW Midstream peer group; equity market risk premium; company-specific risk premium; and terminal growth rate. Under the market approach, trading multiples of the securities of publicly-traded peer companies were applied to DFW Midstream's estimated future cash flows.

Additional significant inputs used in the option pricing method included the length of holding period, discount for lack of marketability and volatility. We determined the length of holding period primarily based on our Sponsors' expectations as of the grant date. We estimated the discount for lack of marketability and volatility with assistance from a third-party valuation firm. We estimated the discount for lack of marketability using a protective put methodology. The protective put methodology consisted of estimating the cost to insure an investment in the DFW Net Profits Interests over the length of the holding period. Using the Black-Scholes option pricing model, we calculated the cost of a put option for the DFW Net Profits Interests as of the various grant dates. The discount for lack of marketability, in each case, was equal to the put option value divided by the value of the underlying membership interest. We estimated the expected volatility of the DFW Net Profits Interests based on the historical and implied volatilities of the securities of publicly-traded peer companies. We estimated historical volatility based on daily stock price returns over a look-back period commensurate with the length of the holding period for each grant date of DFW Net Profits Interests. We estimated implied volatility based on the average implied volatility of the publicly-traded peer companies using data from Standard & Poor's Capital IQ proprietary research tool. We based the expected volatility conclusions on consideration of both the historical and implied volatilities of the publicly-traded peer companies as of the various grant dates. The inputs we used in the option pricing method for the DFW Net Profits Interests by grant date were as follows:



	July 2010 grant		April 2010 grant		September 2009 grant
Length of holding period restriction (In years)	3.43		3.75		4.25
Discount for lack of marketability	35.9	%	30.9	%	34.8	%
Volatility	53.7	%	49.8	%	52.5	%

Information regarding the amount and grant date fair value of the vested and nonvested DFW Net Profits Interests were as follows:



	Year ended December 31,
	2013				2012				2011
	Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)
	(Dollars in thousands)
Nonvested, beginning of period	0.038	%	$	1,650	1.750	%	$	306	2.850	%	$	295
Repurchased	0.038	%	$	1,650	0.000	%	$	—	0.000	%	$	—
Granted	0.000	%	$	—	0.000	%	$	—	0.000	%	$	—
Vested	0.000	%	$	—	1.644	%	$	256	1.100	%	$	277
Forfeited	0.000	%	$	—	0.069	%	$	765	0.400	%	$	220
Nonvested, end of period	0.000	%	$	—	0.038	%	$	1,650	1.750	%	$	306

Vested, end of period	0.000	%	$	—	4.294	%	$	257	2.650	%	$	258

We recognized non-cash compensation expense ratably over the four-year vesting period. Non-cash compensation expense, related to the DFW Net Profits Interests, recognized within general and administrative expense was as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Non-cash compensation expense	$	17	$	688	$	2,171

For the year ended December 31, 2011, non-cash compensation expense also included approximately $0.6 million of expense related to 2010 and 2009. During the year ended December 31, 2011, the Predecessor modified the awards to remove a rate of return payout hurdle. As a result of the modification, we valued the Class B Units immediately prior to and following the modification to determine incremental compensation expense. The modification resulted in the immediate recognition of $1.4 million of expense attributed to the previously vested Class B Units. This amount was included in compensation expense for the year ended December 31, 2011.

SMP Net Profits Interests. In connection with the formation of Summit Investments in 2009, up to 7.5% of total membership interests were authorized for issuance. SMP Net Profits Interests participate in distributions upon time vesting and the achievement of certain distribution targets to Class A members or higher priority vested SMP Net Profits Interests. The SMP Net Profits Interests are accounted for as compensatory awards. Additional SMP Net Profits Interests were granted in April 2010, April 2011, October 2011 and January 2012. All grants vest ratably over five years and provide for accelerated vesting in certain limited circumstances, including a qualifying termination following a change in control (as defined in the underlying award agreement and Summit LLC Agreement). As of December 31, 2012, 6.355% of SMP Net Profits Interests had been granted to certain members of management, and no SMP Net Profits Interests had been forfeited. The SMP Net Profits Interests were retained by the Predecessor and as such are not reflected in SMLP's financial statements subsequent to the IPO.

We determined the fair value of the SMP Net Profits Interests as of the respective grant dates with assistance from a third-party valuation expert. The 2012 and 2011 awards were valued contemporaneously within the year issued, and the 2009 and 2010 awards were valued retrospectively in 2011. We valued the SMP Net Profits Interests utilizing an option pricing method, which models the Class A and Class B membership interests as call options on the underlying equity value of Summit Investments and considers the rights and preferences of each class of equity in order to allocate a fair value to each class.

A significant input of the option pricing method is the enterprise value of Summit Investments. We estimated enterprise value utilizing a combination of the income and market approaches. The income approach utilized the discounted cash flow method, whereby we applied a discount rate to estimated future cash flows of Summit Investments. Key inputs include forecasted gathering volumes; revenues and costs; unlevered equity betas of Summit Investments' peer group; equity market risk premium; company-specific risk premium; and terminal growth rate. Under the market approach, we applied trading multiples of the securities of publicly-traded peer companies to Summit Investments' estimated future cash flows.

Additional significant inputs used in the option pricing method include length of holding period, discount for lack of marketability and volatility. The length of holding period was primarily determined based upon our Sponsors' expectations as of the grant date. We estimated the discount for lack of marketability and volatility with assistance from a third-party valuation firm. We estimated the discount for lack of marketability using a protective put methodology. The protective put methodology consisted of estimating the cost to insure an investment in the SMP Net Profits Interests over the length of the holding period. Using the Black-Scholes option pricing model, we calculated the cost of a put option for the SMP Net Profits Interests as of the various grant dates. The discount for lack of marketability, in each case, is equal to the put option value divided by the value of the underlying membership interest. We estimated the expected volatility of the SMP Net Profits Interests based on the historical and implied volatilities of the securities of publicly-traded peer companies. We estimated historical volatility based on daily stock price returns over a look-back period commensurate with the length of the holding period for each grant of SMP Net Profits Interests. We estimated implied volatility based on the average implied volatility of the publicly-traded peer companies using data from Standard & Poor's Capital IQ proprietary research tool. We based the expected volatility conclusions on consideration of both the historical and implied volatilities of the publicly-traded peer companies as of the various grant dates.

The inputs used in the option pricing method for the SMP Net Profits Interests by grant date were as follows:



	January 2012 grant		October 2011 grant		April 2011 grant		April 2010 grant		September 2009 grant
Length of holding period restriction (In years)	2.93		3.21		4.75		3.75		4.25
Discount for lack of marketability	24.0	%	33.1	%	29.6	%	30.9	%	34.8	%
Volatility	37.0	%	49.3	%	43.2	%	49.8	%	52.5	%

Information regarding the amount and grant-date fair value of the vested and nonvested SMP Net Profits Interests for the periods in which they were reflected in our financial results was as follows:



	Year ended December 31,
	2012				2011
	Percentage Interest		Weighted-average grant date fair value (per 1.0% of SMP Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of SMP Net Profits Interest)
	(Dollars in thousands)
Nonvested, beginning of period	3.958	%	$	1,003	2.944	%	$	601
Granted	0.500	%	$	1,780	2.000	%	$	1,505
Vested	1.271	%	$	965	0.986	%	$	818
Nonvested, end of period	3.187	%	$	1,140	3.958	%	$	1,003

Vested, end of period	3.168	%	$	788	1.897	%	$	669

We recognized non-cash compensation expense ratably over the vesting period. Non-cash compensation expense, related to the SMP Net Profits Interests, recognized in general and administrative expense for the periods in which they were reflected in our financial results was as follows:



	Year ended December 31,
	2012		2011
	(In thousands)
Non-cash compensation expense	$	919	$	1,269

For the year ended December 31, 2011, non-cash compensation expense also included approximately $0.5 million of expense related to 2010 and 2009.

CONCENTRATIONS OF RISK

12 Months Ended

Dec. 31, 2013

Risks and Uncertainties [Abstract]

CONCENTRATIONS OF RISK

Financial instruments that potentially subject us to concentrations of credit risk consist of cash and accounts receivable. We maintain our cash in bank deposit accounts that, at times, may exceed federally insured limits. We have not experienced any losses in such accounts and do not believe we are exposed to any significant risk.

Accounts receivable are primarily from natural gas producers shipping natural gas. This industry concentration has the potential to impact our overall exposure to credit risk, either positively or negatively, in that our customers may be similarly affected by changes in economic, industry or other conditions. We monitor the creditworthiness of our counterparties and generally require letters of credit for receivables from counterparties that are judged to have sub-standard credit, unless the credit risk can otherwise be mitigated.

Counterparties accounting for more than 10% of total revenues were as follows:



	Year ended December 31,
	2013		2012		2011
Revenue:
Counterparty A	22	%	28	%	*
Counterparty B	18	%	20	%	34	%
Counterparty C	*		12	%	17	%
Counterparty D	*		*		12	%
Counterparty E	*		*		10	%

__________

* Less than 10%

Counterparties accounting for more than 10% of total accounts receivable were as follows:



	December 31,
	2013		2012
Accounts receivable:
Counterparty A	44	%	38	%
Counterparty B	13	%	24	%
Counterparty C	—	%	*
Counterparty D	*		*
Counterparty E	*		*

__________

* Less than 10%

RELATED-PARTY TRANSACTIONS

12 Months Ended

Dec. 31, 2013

RELATED-PARTY TRANSACTIONS

Recent Acquisitions and Partners' Capital Issuances. See Notes 5, 6 and 13 for disclosure of the purchase of Bison Midstream from SMP Holdings and the issuance of common units and general partner interests to SMP Holdings in connection with the Bison Drop Down and the Mountaineer Acquisition.

General and Administrative Expense Allocation. Our general partner and its affiliates do not receive a management fee or other compensation in connection with the management of our business, but will be reimbursed for expenses incurred on our behalf. Under our partnership agreement, we reimburse our general partner and its affiliates for certain expenses incurred on our behalf, including, without limitation, salary, bonus, incentive compensation and other amounts paid to our general partner's employees and executive officers who perform services necessary to run our business. In addition, we reimburse our general partner for compensation, travel and entertainment expenses for the directors serving on the board of directors of our general partner and the cost of director and officer liability insurance. Our partnership agreement provides that our general partner will determine in good faith the expenses that are allocable to us.

The payable to our general partner for expenses that were paid on our behalf and the receivable from the general partner for expenses that we paid that were not allocated to the Partnership were as follows:



	December 31,
	2013		2012
	(In thousands)
Due to affiliate	$	653	$	—
Due from affiliate	—		774

Expenses incurred and allocated to us by the general partner under our partnership agreement were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
General and administrative expense allocation	$	3,914	$	1,200	$	—

Electricity Management Services Agreement. We entered into a consulting arrangement with EquiPower Resources Corp. to assist with managing DFW Midstream's electricity price risk. EquiPower Resources Corp. is an affiliate of Energy Capital Partners and is also the employer of a director of our general partner. Amounts paid for such services were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Payments for electricity management consulting services	$	199	$	204	$	11

Engineering Services Agreement. We entered into an engineering services arrangement with IPS Engineering/EPC. IPS Engineering/EPC is an affiliate of Energy Capital Partners. We paid $0.2 million for such services during the year ended December 31, 2013.

Promissory Notes Payable to Sponsors. In conjunction with the Grand River Transaction, we executed $200.0 million of promissory notes, on an unsecured basis, with the Sponsors. The notes had an 8% interest rate and were scheduled to mature in October 2013. In May 2012, we borrowed $163.0 million under the revolving credit facility and used a portion of the same borrowings to prepay $160.0 million principal amount of the promissory notes payable to the Sponsors. Then in July 2012, we borrowed an additional $50.0 million under the revolving credit facility, a portion of which was used to pay the remaining $49.2 million principal amount of the promissory notes payable to Sponsors (inclusive of accrued pay-in-kind interest).

In accordance with the terms of the underlying note agreement, prior to their repayment in July 2012, we elected to make all interest payments on the note in kind. The amount of interest paid in kind and accrued to the balance of the notes for year ended December 31, 2012, was approximately $6.3 million, of which we capitalized $0.9 million of interest expense related to costs incurred on capital projects under construction.

Diligence Expenses. In the past, the Sponsors reimbursed Summit Investments for transactional due diligence expenses related to proposed transactions that were not completed. As of December 31, 2011, we had a receivable from the Sponsors of $1.3 million for similar expenses. During the year ended December 31, 2012, we were reimbursed $0.3 million, while $1.0 million was not paid.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

BENEFIT PLAN	12 Months Ended
BENEFIT PLAN	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
BENEFIT PLAN	BENEFIT PLAN We established a defined contribution benefit plan for our employees in 2009. The expense associated with this plan was approximately $0.4 million in 2013, $0.2 million in 2012, and $0.1 million in 2011.

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Operating Leases. We lease various office space to support our operations and have determined that our leases are operating leases. Total rent expense related to operating leases, which is recognized in general and administrative expenses, was as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Total rent expense	$	1,127	$	724	$	489

The schedule of future minimum lease payments for operating leases that had initial or remaining noncancelable lease terms in excess of one year as of December 31, 2013 was as follows:



	Operating leases
	(In thousands)
2014	$	1,032
2015	1,013
2016	974
2017	707
2018	522

Legal Proceedings. The Partnership is involved in various litigation and administrative proceedings arising in the normal course of business. In the opinion of management, any liabilities that may result from these claims would not individually or in the aggregate have a material adverse effect on its financial position or results of operations.

ACQUISITIONS

12 Months Ended

Dec. 31, 2013

Business Combinations [Abstract]

Acquisitions

ACQUISITIONS

Bison Gas Gathering System. On February 15, 2013, Summit Investments acquired BTE and subsequently contributed it to SMP Holdings. On June 4, 2013, SMP Holdings entered into a purchase and sale agreement with SMLP whereby SMLP acquired the Bison Gas Gathering system. The Bison Gas Gathering system was carved out from BTE and primarily gathers natural gas production from Mountrail and Burke counties in North Dakota under long-term contracts ranging from five years to 15 years. The weighted-average life of the acquired contracts was 12 years upon acquisition.

For additional information, see Notes 1, 5 and 6.

Summit Investments accounted for its purchase of BTE (the "BTE Transaction") under the acquisition method of accounting, whereby the various gathering systems' identifiable tangible and intangible assets acquired and liabilities assumed were recorded based on their fair values as of February 15, 2013. The intangible assets that were acquired are composed of gas gathering agreement contract values and right-of-way easements. Their fair values were determined based upon assumptions related to future cash flows, discount rates, asset lives, and projected capital expenditures to complete the system.

Because the Bison Drop Down was executed between entities under common control, SMLP recognized the acquisition of the Bison Gas Gathering system at historical cost which reflected Summit Investments recent fair value accounting for the BTE Transaction. Furthermore, due to the common control aspect, the Bison Drop Down was accounted for by SMLP on an “as if pooled” basis for all periods in which common control existed. Common control began on February 15, 2013 concurrent with Summit Investments' acquisition of BTE.

The fair values of the assets acquired and liabilities assumed as of February 15, 2013, were as follows (in thousands):



Purchase price assigned to Bison Gas Gathering system			$	303,168
Current assets	$	5,705
Property, plant, and equipment	85,477
Intangible assets	164,502
Other noncurrent assets	2,187
Total assets acquired	257,871
Current liabilities	6,112
Other noncurrent liabilities	2,790
Total liabilities assumed	$	8,902
Net identifiable assets acquired			248,969
Goodwill			$	54,199

We believe that the goodwill recorded represents the incremental value of future cash flow potential attributed to estimated future gathering services within the Williston Basin.

The Bison Drop Down closed on June 4, 2013. The total acquisition purchase price of $248.9 million was funded with $200.0 million of borrowings under SMLP’s revolving credit facility and the issuance of $47.9 million of SMLP common units to SMP Holdings and $1.0 million of general partner interests to SMLP’s general partner. SMP Holdings had a net investment in the Bison Gas Gathering system of $303.2 million and received total consideration of $248.9 million from SMLP. As a result, SMLP recognized a capital contribution from SMP Holdings for the contribution of net assets in excess of consideration paid. See Notes 5 and 6 for additional information.

As noted above, SMLP's acquisition of the Bison Gas Gathering system was a transaction between commonly controlled entities which required that SMLP account for the acquisition in a manner similar to a pooling of interests. As a result, the historical financial statements of the Partnership and the Bison Gas Gathering system have been combined to reflect the historical operations, financial position and cash flows from the date common control began in February 2013. Revenues and net income for the previously separate entities and the combined amounts for the year ended December 31, 2013, as presented in these consolidated financial statements follow.



	Year ended December 31, 2013
	(In thousands)
SMLP revenues	$	225,192
Bison Gas Gathering system revenues	17,614
Combined revenues	$	242,806

SMLP net income	$	43,584
Bison Gas Gathering system net income	52
Combined net income	$	43,636

See Notes 1, 5 and 6 for additional information.

Mountaineer Midstream. We completed the acquisition of Mountaineer Midstream from MarkWest for $210.0 million on June 21, 2013. The Mountaineer Midstream natural gas gathering and compression assets are located in the Appalachian Basin which includes the Marcellus Shale formation primarily in Doddridge County in northern West Virginia. The Mountaineer Midstream system consists of newly constructed, high-pressure gas gathering pipelines, certain rights-of-way associated with the pipeline, and two compressor stations. The assets gather natural gas under a long-term, fee-based contract with an affiliate of Antero Resources Corp. The life of the acquired contract was 13 years upon acquisition.

The Mountaineer Acquisition was funded with $110.0 million of borrowings under the Partnership's revolving credit agreement and the issuance of $100.0 million of common and general partner interests to SMP Holdings. For the year ended December 31, 2013, SMLP recorded $9.6 million of revenue and $2.3 million of net income related to Mountaineer Midstream.

SMLP accounted for the Mountaineer Acquisition under the acquisition method of accounting. As of June 30, 2013, we preliminarily assigned the full $210.0 million purchase price to property plant and equipment. During the third quarter of 2013, we received additional information and, as a result, preliminarily assigned $158.3 million of the purchase price to property, plant and equipment, $27.1 million to contract intangibles, $6.5 million to rights-of-way and $18.1 million to goodwill. During the fourth quarter of 2013, we received additional information from MarkWest and finalized the purchase price allocation.

The final fair values of the assets acquired and liabilities assumed as of June 21, 2013, were as follows (in thousands):



Purchase price assigned to Mountaineer Midstream			$	210,000
Property, plant, and equipment	$	163,661
Gas gathering agreement contract intangibles	24,019
Rights-of-way	6,109
Total assets acquired	193,789
Total liabilities assumed	$	—
Net identifiable assets acquired			193,789
Goodwill			$	16,211

See Notes 1, 5 and 6 for additional information.

Grand River Gathering. In September 2011, we entered into a purchase and sale agreement with Encana Oil & Gas (USA) Inc., a subsidiary of Encana Corporation ("Encana"), to acquire certain natural gas gathering pipeline, dehydration and compression assets in the Piceance Basin in western Colorado (the "Grand River Transaction"). These assets gather production from the Mamm Creek, Orchard, and South Parachute fields in the area around Rifle, Colorado under long-term contracts ranging from 10 years to 25 years. The weighted-average life of these contracts was 12.8 years upon acquisition. The acquired assets included approximately 260 miles of pipeline and approximately 90,000 horsepower of compression facilities. In addition to the acquisition of Grand River Gathering, we have a contractual relationship with Encana related to the development of midstream infrastructure to support Encana’s emerging Mancos and Niobrara shale developments.

The Grand River Transaction closed on October 27, 2011, with an effective date of October 1, 2011, and was funded through an equity contribution of $410.0 million and an aggregate of $200.0 million in promissory notes from the Sponsors. We accounted for the Grand River Transaction under the acquisition method of accounting, whereby the total purchase price was allocated to Grand River Gathering's identifiable tangible and intangible assets acquired and liabilities assumed based on their fair values as of October 27, 2011. The intangible assets that were acquired are composed of gas gathering agreement contract values and right-of-way easements. Their fair values were determined based upon assumptions related to future cash flows, discount rates, asset lives, and projected capital expenditures to complete the Grand River Gathering system.

During the second quarter of 2012, we received the remaining information needed to value the acquired construction work in process and the intangible assets and then finalized its determination of the assets acquired and liabilities assumed of Grand River Gathering as well as its purchase price. As a result, we retrospectively recorded an adjustment to decrease construction work in process by $4.7 million and decrease intangible assets by $37.9 million. We also recognized deferred revenue related to minimum volume commitment payments received prior to the acquisition of Grand River Gathering. These amounts can be used by the customer to offset gathering fees in one or more subsequent periods to the extent that such customer’s throughput volumes in subsequent periods exceed its minimum volume commitment. Additionally, net working capital was recorded as other current liabilities and represents the final settlement of the remaining assets acquired and liabilities assumed. These adjustments to the preliminary purchase price and the allocation to the assets acquired and liabilities assumed resulted in the recognition of goodwill totaling $45.5 million.

The final purchase price allocation has been recorded and presented on a retrospective basis. We believe that the goodwill recorded upon the finalization of the allocation represents the incremental value of future cash flow potential attributed to estimated future gathering services within the emerging Mancos and Niobrara shale developments.

The final fair values of the assets acquired and liabilities assumed as of October 27, 2011, were as follows (in thousands):



Purchase price assigned to Grand River Gathering			$	590,210
Property, plant, and equipment	$	295,240
Gas gathering agreement contract intangibles	244,100
Rights-of-way	8,016
Total assets acquired	547,356
Deferred revenue	1,770
Other current liabilities	854
Total liabilities assumed	$	2,624
Net identifiable assets acquired			544,732
Goodwill			$	45,478

Unaudited Pro Forma Financial Information. The following unaudited pro forma financial information assumes that the acquisitions of Bison Midstream and Mountaineer Midstream occurred on January 1, 2012. The pro forma results for Bison Midstream were derived from revenues and net income in 2013 and 2012. The pro forma results for Mountaineer Midstream were derived from revenues and net income in 2013. Mountaineer Midstream was not operational until November 2012. The pro forma adjustments also reflect the impact of $310.0 million of incremental borrowings on our revolving credit facility and incremental depreciation and amortization expense associated with the acquired property, plant and equipment and contract intangibles as a result of the application of fair value accounting. Pro forma net income for the year ended December 31, 2013 has been adjusted to remove the impact of $2.5 million of nonrecurring transaction costs incurred during the year ended December 31, 2013.



	Year ended December 31,
	2013			2012
	(In thousands)
Total Bison Midstream and Mountaineer Midstream revenues included in consolidated revenues	$	60,323		$	—
Total Bison Midstream and Mountaineer Midstream net income included in consolidated net income	(457		)	—

Pro forma total revenues	$	254,957		$	203,093
Pro forma net income	40,661			32,167

Pro forma common EPU - basic and diluted	$	0.74		0.29
Pro forma subordinated EPU - basic and diluted	0.74			0.29

The following unaudited pro forma financial information assumes that we acquired the Grand River system on January 1, 2010. The pro forma results for Grand River Gathering were derived by annualizing the actual operating results for Grand River Gathering that were recorded in 2011. Pro forma net income for the year ended December 31, 2011 has been adjusted to remove the impact of $3.2 million of nonrecurring transaction costs incurred during the year ended December 31, 2011.



	Year ended December 31, 2011
	(In thousands)
Total Grand River revenues included in consolidated revenues	$	12,824
Total Grand River net income included in consolidated net income	2,660

Pro forma total revenues	$	167,671
Pro forma net income	54,405

The unaudited pro forma financial information presented above is not necessarily indicative of (i) what our financial position or results of operations would have been if the acquisitions of Bison Midstream and Mountaineer Midstream had occurred on January 1, 2012 or if the Grand River Transaction had occurred on January 1, 2010, or (ii) what SMLP’s financial position or results of operations will be for any future periods.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 4
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1500-128463

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1524-128463

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=7488404&loc=d3e6996-128479

+ Details

SUBSQUENT EVENT	12 Months Ended
SUBSQUENT EVENT	Dec. 31, 2013
Subsequent Events [Abstract]
SUBSQUENT EVENT	SUBSQUENT EVENT On March 8, 2014, Summit Investments offered 100% of its interests in Red Rock Gathering Company, LLC ("Red Rock") to the Partnership in exchange for total cash consideration of $305.0 million, subject to customary working capital adjustments (the "Red Rock Drop Down"). The Red Rock Drop Down is expected to close by March 31, 2014. Because of the common control aspects in a drop down transaction, the Red Rock acquisition is expected to be deemed a transaction between entities under common control and, as such, will be accounted for on an “as if pooled” basis for all periods in which common control existed. Upon closing the acquisition of Red Rock, SMLP’s financial results will retrospectively include Red Rock’s financial results for all periods ending after October 23, 2012.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Reclassification

Fair Value of Financial Instruments


•	Level 1. Inputs represent quoted prices in active markets for identical assets or liabilities;

•


•	Level 3. Inputs that are not observable from objective sources, such as management’s internally developed assumptions used in pricing an asset or liability (for example, an estimate of future cash flows used in management’s internally developed present value of future cash flows model that underlies the fair value measurement).

Nonfinancial assets and liabilities initially measured at fair value include those acquired and assumed in connection with third-party business combinations.

A summary of the estimated fair value for financial instruments follows.



	December 31, 2013				December 31, 2012
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	286,000	$	286,000	$	199,230	$	199,230
Senior notes	300,000		314,625		—		—

Intangible Assets and Noncurrent Liability

Other Noncurrent Assets

Revenue Recognition

We obtain access to natural gas and provide services principally under contracts that contain one or both of the following arrangements:

•



	Current		Noncurrent
	(In thousands)
Deferred revenue, January 1, 2012	$	—	$	1,770
Additions	865		9,129
Deferred revenue, December 31, 2012	865		10,899
Additions (1)	1,555		18,784
Less: revenue recognized due to expiration	865		—
Deferred revenue, December 31, 2013	$	1,555	$	29,683

__________

(1) Noncurrent includes amounts recognized in connection with the Bison Drop Down.

Unit Based Compensation

Income Taxes

Earnings per Unit

Comprehensive Income

Comprehensive Income. Comprehensive income is the same as net income for all periods presented.

Environmental Matters

Recent Accounting Pronouncements

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2013

Accounting Policies [Abstract]

Summary of Estimated Fair Value for Financial instruments

A summary of the estimated fair value for financial instruments follows.



	December 31, 2013				December 31, 2012
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	286,000	$	286,000	$	199,230	$	199,230
Senior notes	300,000		314,625		—		—

Deferred Revenue, by Arrangement, Disclosure

A rollforward of current and noncurrent deferred revenue follows.



	Current		Noncurrent
	(In thousands)
Deferred revenue, January 1, 2012	$	—	$	1,770
Additions	865		9,129
Deferred revenue, December 31, 2012	865		10,899
Additions (1)	1,555		18,784
Less: revenue recognized due to expiration	865		—
Deferred revenue, December 31, 2013	$	1,555	$	29,683

__________

(1) Noncurrent includes amounts recognized in connection with the Bison Drop Down.

PROPERTY, PLANT, AND EQUIPMENT, NET (Tables)

12 Months Ended

Dec. 31, 2013

Property, Plant and Equipment [Abstract]

Schedule of property, plant, and equipment, net

Details on property, plant, and equipment, net were as follows:



	Useful lives (In years)	December 31,
	Useful lives (In years)	2013			2012
	(Dollars in thousands)
Gas gathering systems	30	$	634,177		$	427,449
Compressor stations and compression equipment	30	351,560			237,618
Construction in progress	n/a	51,023			45,919
Other	4-15	7,451			4,524
Total		1,044,211			715,510
Accumulated depreciation		(63,870		)	(33,517		)
Property, plant, and equipment, net		$	980,341		$	681,993

Schedule of depreciation expense related to property, plant and equipment and capitalized interest

Depreciation expense related to property, plant, and equipment and capitalized interest were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Depreciation expense	$	30,353	$	21,337	$	8,595
Capitalized interest	4,209		2,784		3,362

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL (Tables)

12 Months Ended

Dec. 31, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of identifiable intangible assets and a noncurrent liability, which are subject to amortization

Identifiable intangible assets and the noncurrent liability, which are subject to amortization, were as follows:



	December 31, 2013
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(6,315	)	$	17,880
Contract intangibles	12.5	426,464		(43,158		)	383,306
Rights-of-way	28.3	56,487		(4,679		)	51,808
Total amortizable intangible assets		$	507,146	$	(54,152	)	$	452,994

Unfavorable gas gathering contract	10.0	$	10,962	$	(4,588	)	$	6,374



	December 31, 2012
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(4,237	)	$	19,958
Contract intangibles	12.4	244,100		(14,504		)	229,596
Rights-of-way	28.3	38,848		(2,862		)	35,986
Total amortizable intangible assets		$	307,143	$	(21,603	)	$	285,540

Unfavorable gas gathering contract	10.0	$	10,962	$	(3,542	)	$	7,420

Schedule of recognized amortization expense within the statements of operations

We recognized amortization expense as follows:



	Year ended December 31,
	2013			2012			2011
	(In thousands)
Amortization expense – favorable gas gathering contracts	$	2,078		$	1,715		$	1,718
Amortization expense – contract intangibles	28,654			12,642			1,862
Amortization expense – rights-of-way	1,817			1,321			908
Amortization expense – unfavorable gas gathering contract	(1,046		)	(1,524		)	(1,410		)

Schedule of estimated aggregate amortization of intangible assets and the noncurrent liability for each of the five succeeding fiscal years

The estimated aggregate annual amortization of intangible assets and noncurrent liability expected to be recognized as of December 31, 2013 for each of the five succeeding fiscal years follows.



	Assets		Liabilities
	(In thousands)
2014	$	37,893	$	1,549
2015	40,912		1,650
2016	41,167		1,571
2017	39,903		1,604
2018	39,448		—

Schedule of Goodwill

A rollforward of the consolidated balance of goodwill follows (in thousands).



Goodwill, December 31, 2012 and 2011	$	45,478
Goodwill recognized in connection with the Bison Drop Down	54,199
Goodwill preliminarily recognized in connection with the Mountaineer Acquisition	18,089
Goodwill adjustment recognized in connection with finalizing accounting for the Mountaineer Acquisition and other	(1,878		)
Goodwill, December 31, 2013	$	115,888

LONG-TERM DEBT (Tables)

12 Months Ended

Dec. 31, 2013

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

Long-term debt consisted of the following:



	December 31,
	2013		2012
	(In thousands)
Variable rate senior secured revolving credit facility (2.42% at December 31, 2013 and 2.98% at December 31, 2012) due November 2018	$	286,000	$	199,230
7.50% Senior unsecured notes due July 2021	300,000		—
Total long-term debt	$	586,000	$	199,230

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Tables)

12 Months Ended

Dec. 31, 2013

Business Acquisition [Line Items]

Schedule of Partner Units Activity

A rollforward of the number of common limited partner, subordinated limited partner and general partner units follows.



	Common	Subordinated	General partner	Total
Units, January 1, 2012	—	—	—	—
Units issued to the public in connection with the IPO	14,380,000	—	—	14,380,000
Units issued to affiliates in connection with the IPO	10,029,850	24,409,850	996,320	35,436,020
Units issued	2,577	—	—	2,577
Units, December 31, 2012	24,412,427	24,409,850	996,320	49,818,597
Units issued to affiliates in connection with the Bison Drop Down	1,553,849	—	31,711	1,585,560
Units issued to affiliates in connection with the Mountaineer Acquisition	3,107,698	—	63,422	3,171,120
Units issued	5,892	—	—	5,892
Units, December 31, 2013	29,079,866	24,409,850	1,091,453	54,581,169

Schedule of partnership target distributions



	Total quarterly distribution per unit target amount	Marginal percentage interest in distributions
	Total quarterly distribution per unit target amount	Unitholders	General partner
Minimum quarterly distribution	$0.40	98.0%	2.0%
First target distribution	$0.40 up to $0.46	98.0%	2.0%
Second target distribution	above $0.46 up to $0.50	85.0%	15.0%
Third target distribution	above $0.50 up to $0.60	75.0%	25.0%
Thereafter	above $0.60	50.0%	50.0%

Details of Cash Distributions

Details of cash distributions declared follow.



Attributable to the quarter ended	Payment date	Per-unit distribution		Cash paid (or payable) to common unitholders		Cash paid (or payable) to subordinated unitholders		Cash paid (or payable) to general partner ⁽¹⁾		Total distribution
		(Dollars in thousands, except per-unit amounts)
December 31, 2012	February 14, 2013	$	0.4100	$	10,009	$	10,008	$	408	$	20,425
March 31, 2013	May 15, 2013	0.4200		10,253		10,252		418		20,923
June 30, 2013	August 14, 2013	0.4350		12,647		10,618		475		23,740
September 30, 2013	November 14, 2013	0.4600		13,377		11,229		502		25,108
December 31, 2013	February 14, 2014	0.4800		13,958		11,717		691		26,366

__________

Bison Midstream

Business Acquisition [Line Items]

Schedule of Business Acquisition

In exchange for its $305.4 million net investment in Bison Midstream, SMLP paid SMP Holdings and the general partner total cash and unit consideration of $248.9 million. As a result of the contribution of net assets in excess of consideration, SMLP recognized a capital contribution from SMP Holdings. The details of total cash and unit consideration as well as the calculation of the capital contribution and its allocation to partners' capital follow (dollars in thousands).



SMP Holdings' net investment in Bison Midstream			$	305,449
Aggregate cash paid to SMP Holdings	$	200,000
Issuance of 1,553,849 SMLP common units to SMP Holdings	47,936
Issuance of 31,711 SMLP general partner units to the general partner	978
Total consideration			248,914
SMP Holdings' contribution of net assets in excess of consideration			$	56,535

Allocation of capital contribution:
General partner interest	$	1,131
Common limited partner interest	28,558
Subordinated limited partner interest	26,846
Partners' capital allocation			$	56,535

The fair values of the assets acquired and liabilities assumed as of February 15, 2013, were as follows (in thousands):



Purchase price assigned to Bison Gas Gathering system			$	303,168
Current assets	$	5,705
Property, plant, and equipment	85,477
Intangible assets	164,502
Other noncurrent assets	2,187
Total assets acquired	257,871
Current liabilities	6,112
Other noncurrent liabilities	2,790
Total liabilities assumed	$	8,902
Net identifiable assets acquired			248,969
Goodwill			$	54,199

Mountaineer Midstream

Business Acquisition [Line Items]

Schedule of Business Acquisition

The allocation and valuation of units issued to SMP Holdings and the general partner to partially fund the Mountaineer Acquisition follow (dollars in thousands).



Issuance of 3,107,698 SMLP common units to SMP Holdings	$	98,000
Issuance of 63,422 SMLP general partner units to the general partner	2,000
Issuance of units in connection with the Mountaineer Acquisition	$	100,000

The final fair values of the assets acquired and liabilities assumed as of June 21, 2013, were as follows (in thousands):



Purchase price assigned to Mountaineer Midstream			$	210,000
Property, plant, and equipment	$	163,661
Gas gathering agreement contract intangibles	24,019
Rights-of-way	6,109
Total assets acquired	193,789
Total liabilities assumed	$	—
Net identifiable assets acquired			193,789
Goodwill			$	16,211

EARNINGS PER UNIT (Tables)

12 Months Ended

Dec. 31, 2013

Earnings Per Share [Abstract]

Schedule of earnings per Unit

The following table presents details on EPU.



	Year ended December 31,
	2013		2012 ⁽¹⁾
	(Dollars in thousands, except per-unit amounts)
Net income	$	43,636	$	41,726
Less: net income attributable to the pre-IPO period	—		24,112
Less: net income attributable to SMP Holdings	52		—
Net income attributable to SMLP	43,584		17,614
Less: net income attributable to general partner, including IDRs	1,035		352
Net income attributable to limited partners	$	42,549	$	17,262

Numerator for basic and diluted EPU:
Allocation of net income among limited partner interests:
Net income attributable to common units	$	23,227	$	8,632
Net income attributable to subordinated units	19,322		8,630
Net income attributable to limited partners	$	42,549	$	17,262

Denominator for basic and diluted EPU:
Weighted-average common units outstanding – basic	26,951,346		24,412,427
Less: effect of non-vested phantom units and non-vested restricted units	150,133		131,558
Weighted-average common units outstanding – diluted	27,101,479		24,543,985

Weighted-average subordinated units outstanding – basic and diluted	24,409,850		24,409,850

Net income per limited partner unit:
Common unit – basic	$	0.86	$	0.35
Common unit – diluted	$	0.86	$	0.35
Subordinated unit – basic and diluted	$	0.79	$	0.35

__________

(1) Calculated for the period from October 1, 2012 to December 31, 2012

UNIT-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2013

Phantom and restricted units

MEMBERSHIP INTERESTS

Schedule of activity

The following table presents phantom and restricted unit activity:



	Units		Weighted-average grant date fair value
Nonvested phantom and restricted units, January 1, 2012	—		$	—
Phantom units granted	125,000		$	20.00
Restricted units granted	6,558		$	20.23
Nonvested phantom and restricted units, December 31, 2012	131,558		$	20.00
Phantom units granted	155,330		$	26.33
Restricted units granted	835		$	27.50
Phantom units forfeited	(4,041	)	$	25.99
Nonvested phantom and restricted units, December 31, 2013	283,682		$	23.41

Long-term Incentive Plan

MEMBERSHIP INTERESTS

Schedule of non-cash compensation expense recognized in general and administrative expense

Unit-based compensation recognized in general and administrative expense related to awards under the LTIP was as follows:



	Year ended December 31, 2013
	2013		2012		2011
	(In thousands)
SMLP unit-based compensation	$	2,999	$	269	$	—

DFW Net Profits Interests

MEMBERSHIP INTERESTS

Schedule of activity



	July 2010 grant		April 2010 grant		September 2009 grant
Length of holding period restriction (In years)	3.43		3.75		4.25
Discount for lack of marketability	35.9	%	30.9	%	34.8	%
Volatility	53.7	%	49.8	%	52.5	%

Information regarding the amount and grant date fair value of the vested and nonvested DFW Net Profits Interests were as follows:



	Year ended December 31,
	2013				2012				2011
	Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of DFW Net Profits Interest)
	(Dollars in thousands)
Nonvested, beginning of period	0.038	%	$	1,650	1.750	%	$	306	2.850	%	$	295
Repurchased	0.038	%	$	1,650	0.000	%	$	—	0.000	%	$	—
Granted	0.000	%	$	—	0.000	%	$	—	0.000	%	$	—
Vested	0.000	%	$	—	1.644	%	$	256	1.100	%	$	277
Forfeited	0.000	%	$	—	0.069	%	$	765	0.400	%	$	220
Nonvested, end of period	0.000	%	$	—	0.038	%	$	1,650	1.750	%	$	306

Vested, end of period	0.000	%	$	—	4.294	%	$	257	2.650	%	$	258

Schedule of inputs used in the option pricing method

The inputs we used in the option pricing method for the DFW Net Profits Interests by grant date were as follows:



	July 2010 grant		April 2010 grant		September 2009 grant
Length of holding period restriction (In years)	3.43		3.75		4.25
Discount for lack of marketability	35.9	%	30.9	%	34.8	%
Volatility	53.7	%	49.8	%	52.5	%

Schedule of non-cash compensation expense recognized in general and administrative expense



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Non-cash compensation expense	$	17	$	688	$	2,171

SMP Net Profits Interests

MEMBERSHIP INTERESTS

Schedule of activity

Information regarding the amount and grant-date fair value of the vested and nonvested SMP Net Profits Interests for the periods in which they were reflected in our financial results was as follows:



	Year ended December 31,
	2012				2011
	Percentage Interest		Weighted-average grant date fair value (per 1.0% of SMP Net Profits Interest)		Percentage Interest		Weighted-average grant date fair value (per 1.0% of SMP Net Profits Interest)
	(Dollars in thousands)
Nonvested, beginning of period	3.958	%	$	1,003	2.944	%	$	601
Granted	0.500	%	$	1,780	2.000	%	$	1,505
Vested	1.271	%	$	965	0.986	%	$	818
Nonvested, end of period	3.187	%	$	1,140	3.958	%	$	1,003

Vested, end of period	3.168	%	$	788	1.897	%	$	669

Schedule of inputs used in the option pricing method

The inputs used in the option pricing method for the SMP Net Profits Interests by grant date were as follows:



	January 2012 grant		October 2011 grant		April 2011 grant		April 2010 grant		September 2009 grant
Length of holding period restriction (In years)	2.93		3.21		4.75		3.75		4.25
Discount for lack of marketability	24.0	%	33.1	%	29.6	%	30.9	%	34.8	%
Volatility	37.0	%	49.3	%	43.2	%	49.8	%	52.5	%

Schedule of non-cash compensation expense recognized in general and administrative expense

Non-cash compensation expense, related to the SMP Net Profits Interests, recognized in general and administrative expense for the periods in which they were reflected in our financial results was as follows:



	Year ended December 31,
	2012		2011
	(In thousands)
Non-cash compensation expense	$	919	$	1,269

CONCENTRATIONS OF RISK (Tables)

12 Months Ended

Dec. 31, 2013

Revenue | Customer concentration

CONCENTRATIONS OF RISK

Schedule of customers accounting for more than 10% of total revenues

Counterparties accounting for more than 10% of total revenues were as follows:



	Year ended December 31,
	2013		2012		2011
Revenue:
Counterparty A	22	%	28	%	*
Counterparty B	18	%	20	%	34	%
Counterparty C	*		12	%	17	%
Counterparty D	*		*		12	%
Counterparty E	*		*		10	%

__________

* Less than 10%

Accounts receivable | Credit concentration

CONCENTRATIONS OF RISK

Schedule of customers accounting for more than 10% of total revenues

Counterparties accounting for more than 10% of total accounts receivable were as follows:



	December 31,
	2013		2012
Accounts receivable:
Counterparty A	44	%	38	%
Counterparty B	13	%	24	%
Counterparty C	—	%	*
Counterparty D	*		*
Counterparty E	*		*

__________

* Less than 10%

RELATED-PARTY TRANSACTIONS (Tables)

12 Months Ended

Dec. 31, 2013

Schedules of Related Party Transactions

Amounts paid for such services were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Payments for electricity management consulting services	$	199	$	204	$	11



	December 31,
	2013		2012
	(In thousands)
Due to affiliate	$	653	$	—
Due from affiliate	—		774

Expenses incurred and allocated to us by the general partner under our partnership agreement were as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
General and administrative expense allocation	$	3,914	$	1,200	$	—

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2013

Commitments and Contingencies Disclosure [Abstract]

Schedule of total rent expense related to operating leases

Total rent expense related to operating leases, which is recognized in general and administrative expenses, was as follows:



	Year ended December 31,
	2013		2012		2011
	(In thousands)
Total rent expense	$	1,127	$	724	$	489

Schedule of future minimum lease payments for operating leases

The schedule of future minimum lease payments for operating leases that had initial or remaining noncancelable lease terms in excess of one year as of December 31, 2013 was as follows:



	Operating leases
	(In thousands)
2014	$	1,032
2015	1,013
2016	974
2017	707
2018	522

ACQUISITIONS (Tables)

12 Months Ended

Dec. 31, 2013

Business Acquisition [Line Items]

Business Acquisition, Pro Forma Information



	Year ended December 31,
	2013			2012
	(In thousands)
Total Bison Midstream and Mountaineer Midstream revenues included in consolidated revenues	$	60,323		$	—
Total Bison Midstream and Mountaineer Midstream net income included in consolidated net income	(457		)	—

Pro forma total revenues	$	254,957		$	203,093
Pro forma net income	40,661			32,167

Pro forma common EPU - basic and diluted	$	0.74		0.29
Pro forma subordinated EPU - basic and diluted	0.74			0.29

Bison Midstream

Business Acquisition [Line Items]

Fair Value of Assets Acquired and Liabilities Assumed



SMP Holdings' net investment in Bison Midstream			$	305,449
Aggregate cash paid to SMP Holdings	$	200,000
Issuance of 1,553,849 SMLP common units to SMP Holdings	47,936
Issuance of 31,711 SMLP general partner units to the general partner	978
Total consideration			248,914
SMP Holdings' contribution of net assets in excess of consideration			$	56,535

Allocation of capital contribution:
General partner interest	$	1,131
Common limited partner interest	28,558
Subordinated limited partner interest	26,846
Partners' capital allocation			$	56,535

The fair values of the assets acquired and liabilities assumed as of February 15, 2013, were as follows (in thousands):



Purchase price assigned to Bison Gas Gathering system			$	303,168
Current assets	$	5,705
Property, plant, and equipment	85,477
Intangible assets	164,502
Other noncurrent assets	2,187
Total assets acquired	257,871
Current liabilities	6,112
Other noncurrent liabilities	2,790
Total liabilities assumed	$	8,902
Net identifiable assets acquired			248,969
Goodwill			$	54,199

Schedule of Revenue and Net Income Disclosures

Revenues and net income for the previously separate entities and the combined amounts for the year ended December 31, 2013, as presented in these consolidated financial statements follow.



	Year ended December 31, 2013
	(In thousands)
SMLP revenues	$	225,192
Bison Gas Gathering system revenues	17,614
Combined revenues	$	242,806

SMLP net income	$	43,584
Bison Gas Gathering system net income	52
Combined net income	$	43,636

Mountaineer Midstream

Business Acquisition [Line Items]

Fair Value of Assets Acquired and Liabilities Assumed

The allocation and valuation of units issued to SMP Holdings and the general partner to partially fund the Mountaineer Acquisition follow (dollars in thousands).



Issuance of 3,107,698 SMLP common units to SMP Holdings	$	98,000
Issuance of 63,422 SMLP general partner units to the general partner	2,000
Issuance of units in connection with the Mountaineer Acquisition	$	100,000

The final fair values of the assets acquired and liabilities assumed as of June 21, 2013, were as follows (in thousands):



Purchase price assigned to Mountaineer Midstream			$	210,000
Property, plant, and equipment	$	163,661
Gas gathering agreement contract intangibles	24,019
Rights-of-way	6,109
Total assets acquired	193,789
Total liabilities assumed	$	—
Net identifiable assets acquired			193,789
Goodwill			$	16,211

Grand River Gathering, LLC

Business Acquisition [Line Items]

Fair Value of Assets Acquired and Liabilities Assumed

The final fair values of the assets acquired and liabilities assumed as of October 27, 2011, were as follows (in thousands):



Purchase price assigned to Grand River Gathering			$	590,210
Property, plant, and equipment	$	295,240
Gas gathering agreement contract intangibles	244,100
Rights-of-way	8,016
Total assets acquired	547,356
Deferred revenue	1,770
Other current liabilities	854
Total liabilities assumed	$	2,624
Net identifiable assets acquired			544,732
Goodwill			$	45,478

ORGANIZATION, BUSINESS OPERATIONS AND BASIS OF PRESENTATION (Details) $ in Thousands			1 Months Ended		12 Months Ended
	Jun. 04, 2013	Oct. 03, 2012 USD ($) director shares	Jun. 30, 2013 USD ($)	Mar. 31, 2013	Dec. 31, 2013 USD ($) segment shares	Dec. 31, 2012 USD ($) shares	Dec. 31, 2011 USD ($)
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding					29,079,866	24,412,427
General partner interests, units outstanding					1,091,453	996,320
Common units sold in public offering						14,380,000
Net proceeds from the IPO \| $		$ 269,400			$ 0	$ 263,125	$ 0
Repayment of indebtedness \| $			$ 294,200		$ 294,180	$ 160,770	$ 0
Estimated IPO expenses \| $		6,300
Number of operating segments \| segment					4
Number of reportable segments \| segment					1
Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Distributions made to reimburse for certain capital expenditures \| $		88,000
Distributions made in connection with underwriters exercising option to purchase additional units \| $		$ 35,100
Holdings
ORGANIZATION AND BUSINESS OPERATIONS
Cumulative percentage ownership after all transactions		100.00%
DFW Midstream
ORGANIZATION AND BUSINESS OPERATIONS
Cumulative percentage ownership after all transactions		100.00%
Grand River Gathering, LLC
ORGANIZATION AND BUSINESS OPERATIONS
Cumulative percentage ownership after all transactions		100.00%
Summit Midstream Partners Holdings, LLC
ORGANIZATION AND BUSINESS OPERATIONS
Limited partner interest (as a percent)				100.00%
SMP Holdings
ORGANIZATION AND BUSINESS OPERATIONS
General partner interests, units outstanding					1,091,453
Common units \| SMP Holdings
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding					14,691,397
Subordinated units \| SMP Holdings
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding					24,409,850
General partner
ORGANIZATION AND BUSINESS OPERATIONS
General partner interest (as a percent)	2.00%	2.00%		2.00%
General partner units		996,320
Limited Partner \| Common units
ORGANIZATION AND BUSINESS OPERATIONS
Units sold to public for cash in connection with the exercise of the underwriters' option to purchase additional common units		1,875,000
Common units sold in public offering		14,375,000
Limited partner interest sold in public offering (as a percent)		28.90%
Limited Partner \| Common units \| Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Limited partner interest (as a percent)		20.10%
General partner units		10,029,850
Limited Partner \| Subordinated units \| Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Limited partner interest (as a percent)		49.00%
General partner units		24,409,850
Director \| Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Number of related persons to whom common units were granted \| director		2
Director \| Common units
ORGANIZATION AND BUSINESS OPERATIONS
Units granted in connection with IPO pursuant to LTIP		5,000
Phantom Units
ORGANIZATION AND BUSINESS OPERATIONS
Units granted in connection with IPO pursuant to LTIP					155,330	125,000
Phantom Units \| Employees \| Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Units granted in connection with IPO pursuant to LTIP		125,000
Revolving credit facility \| Predecessor
ORGANIZATION AND BUSINESS OPERATIONS
Repayment of indebtedness \| $		$ 140,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility, Carrying value	$ 286,000	$ 199,230
Senior notes, Carrying value	300,000	0
Fair value, Level 2 inputs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility, Estimated fair value (Level 2)	286,000	199,230
Senior notes, Estimated fair value (Level 2)	$ 314,625	$ 0

SUMMARY OF SIGNIFICANT ACCOUNITNG POLICIES (Details 1)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNITNG POLICIES (Details 1)	Dec. 31, 2013	Dec. 31, 2012
Favorable gas gathering contract
Finite-Lived Intangible Assets [Line Items]
Useful lives	18 years 8 months 12 days	18 years 8 months 12 days
Favorable gas gathering contract \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	10 years
Favorable gas gathering contract \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	20 years
Other gas gathering contract \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	10 years
Other gas gathering contract \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	25 years
Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Useful lives	28 years 3 months 18 days	28 years 3 months 18 days
Rights-of-way \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful lives	20 years
Rights-of-way \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful lives	30 years
Gathering systems
Finite-Lived Intangible Assets [Line Items]
Useful lives	30 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Millions			1 Months Ended	12 Months Ended
	Jun. 04, 2013	Oct. 03, 2012	Mar. 31, 2013	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Shortfall payments billed and included in accounts receivable				$ 1.1
General partner
Significant Accounting Policies [Line Items]
General partner interest (as a percent)	2.00%	2.00%	2.00%
Minimum
Significant Accounting Policies [Line Items]
Period to utilize shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC				12 months
Period to utilize the current portion of shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC				1 month
Maximum
Significant Accounting Policies [Line Items]
Period to utilize shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC				8 years
Period to utilize the current portion of shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC				8 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, Beginning balance, Current	$ 865	$ 0
Additions, Current	1,555	865
Less: revenue recognized due to expiration, Current	865
Deferred revenue, Ending balance, Current	1,555	865
Deferred revenue, Beginning balance, Noncurrent	10,899	1,770
Additions, Noncurrent	18,784	9,129
Less: revenue recognized due to expiration, Noncurrent	0
Deferred revenue, Ending balance, Noncurrent	$ 29,683	$ 10,899

PROPERTY, PLANT, AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	$ 1,044,211	$ 715,510
Less accumulated depreciation	(63,870)	(33,517)
Property, plant, and equipment, net	980,341	681,993
Depreciation expense	30,353	21,337	$ 8,595
Capitalized interest	$ 4,209	2,784	$ 3,362
Gas gathering system
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives	30 years
Gross	$ 634,177	427,449
Compressor stations and compression equipment
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives	30 years
Gross	$ 351,560	237,618
Construction in progress
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	51,023	45,919
Other
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	$ 7,451	$ 4,524
Other \| Minimum
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives	4 years
Other \| Maximum
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives	15 years

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL (Details) - USD ($) $ in Thousands			12 Months Ended
	Jun. 21, 2013	Oct. 27, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount			$ 507,146	$ 307,143
Accumulated amortization			(54,152)	(21,603)
Total intangible assets, net			$ 452,994	$ 285,540
Noncurrent liability
Unfavorable gas gathering contract, useful lives			10 years	10 years
Unfavorable contract, Gross Carrying Amount			$ 10,962	$ 10,962
Unfavorable gas gathering contract, Accumulated Amortization			(4,588)	(3,542)
Unfavorable gas gathering contract, Net			6,374	7,420
Amortization expense
Amortization expense - unfavorable contract			(1,046)	(1,524)	$ (1,410)
Assets
2014			37,893
2015			40,912
2016			41,167
2017			39,903
2018			39,448
Liabilities
2014			1,549
2015			1,650
2016			1,571
2017			1,604
2018			0
Goodwill [Roll Forward]
Goodwill, beginning balance			45,478	45,478
Goodwill adjustment recognized in connection with finalizing accounting for the Mountaineer Acquisition and other			(1,878)
Goodwill, ending balance			115,888	45,478	45,478
Mountaineer Midstream
Goodwill [Roll Forward]
Goodwill recognized in connection with acquisitions			18,089
Goodwill, ending balance	$ 16,211
Grand River Gathering, LLC
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 45,500
Goodwill, ending balance		$ 45,478			45,500
Bison Midstream
Goodwill [Roll Forward]
Goodwill recognized in connection with acquisitions			54,199
Goodwill, ending balance			$ 54,200
Favorable gas gathering contract
Finite-Lived Intangible Assets [Line Items]
Useful lives			18 years 8 months 12 days	18 years 8 months 12 days
Gross carrying amount			$ 24,195	$ 24,195
Accumulated amortization			(6,315)	(4,237)
Total intangible assets, net			17,880	19,958
Amortization expense
Amortization expense			$ 2,078	$ 1,715	1,718
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Useful lives			12 years 6 months	12 years 4 months 24 days
Gross carrying amount			$ 426,464	$ 244,100
Accumulated amortization			(43,158)	(14,504)
Total intangible assets, net			383,306	229,596
Amortization expense
Amortization expense			$ 28,654	$ 12,642	1,862
Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Useful lives			28 years 3 months 18 days	28 years 3 months 18 days
Gross carrying amount			$ 56,487	$ 38,848
Accumulated amortization			(4,679)	(2,862)
Total intangible assets, net			51,808	35,986
Amortization expense
Amortization expense			$ 1,817	$ 1,321	$ 908

LONG-TERM DEBT (Details) - USD ($)	1 Months Ended		12 Months Ended
LONG-TERM DEBT (Details) - USD ($)	Nov. 30, 2013	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 31, 2013
REVOLVING CREDIT FACILITY
Revolving credit facility			$ 286,000,000	$ 199,230,000
Senior unsecured notes			300,000,000	0
Total long-term debt			586,000,000	199,230,000
Repayments of Lines of Credit		$ 294,200,000	294,180,000	$ 160,770,000	$ 0
Bison Midstream
REVOLVING CREDIT FACILITY
Revolving credit facility		200,000,000.0
Mountaineer Midstream
REVOLVING CREDIT FACILITY
Revolving credit facility		110,000,000.0
Revolving credit facility
REVOLVING CREDIT FACILITY
Defaults on revolving credit facility			$ 0
Revolving credit facility \| Holdings
REVOLVING CREDIT FACILITY
Variable rate basis			LIBOR
Applicable margin (as a percent)			2.25%
Weighted-average interest rate (as a percent)			2.42%	2.98%
Unused portion under the facility			$ 414,000,000
Commitment fee on unused portion of the facility (as a percent)			0.375%
Period that cumulative lease payment obligations may not exceed specified amount under terms of covenants			12 months
Trailing period used in calculating the ratio of EBITDA to net interest expense			12 months
Trailing period used in calculating the ratio of total indebtedness to consolidated EBITDA			12 months
Revolving credit facility \| Holdings \| Minimum
REVOLVING CREDIT FACILITY
Ratio of consolidated EBITDA to net interest expense			2.5
Revolving credit facility \| Holdings \| Maximum
REVOLVING CREDIT FACILITY
Cumulative lease payment obligations allowable under terms of covenants			$ 30,000,000.0
Ratio of total indebtedness to consolidated EBITDA			5.0
Ratio of total indebtedness to consolidated EBITDA, for a specified period following certain acquisitions			5.5
Period following certain acquisitions, for which higher ratio of total indebtedness to consolidated EBITDA is to be maintained			270 days
Revolving credit facility \| Senior Secured Debt
REVOLVING CREDIT FACILITY
Senior secured revolving credit facility, total commitments	$ 700,000,000.0	600,000,000.0				$ 550,000,000.0
Interest rate reduction	0.75%
Revolving credit facility \| Senior Secured Debt \| Minimum
REVOLVING CREDIT FACILITY
Commitment fee on unused portion of the facility (as a percent)	0.30%
Revolving credit facility \| Senior Secured Debt \| Maximum
REVOLVING CREDIT FACILITY
Commitment fee on unused portion of the facility (as a percent)	0.50%
Revolving credit facility \| Senior Secured Debt \| LIBOR \| Minimum
REVOLVING CREDIT FACILITY
Applicable margin (as a percent)	1.75%
Revolving credit facility \| Senior Secured Debt \| LIBOR \| Maximum
REVOLVING CREDIT FACILITY
Applicable margin (as a percent)	2.75%
Revolving credit facility \| Senior Secured Debt \| Accordion provision
REVOLVING CREDIT FACILITY
Senior secured revolving credit facility, total commitments	$ 200,000,000.0	$ 50,000,000.0

LONG-TERM DEBT (Senior Note) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Jun. 17, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Senior unsecured notes	$ 300,000		$ 0
Senior Notes
Debt Instrument [Line Items]
Senior unsecured notes		$ 300,000
Senior note, stated interest rate		7.50%
Debt issuance costs	$ 7,300
Period to complete exchange offer	365 days
Event of default, period of nonpayment	30 days
Event of default, period of noncompliance with SEC filings	180 days
Event of default, period of noncompliance with indenture agreements	30 days
Event of default, failure to pay judgments (more than)	$ 20,000
Event of default, Percentage of debt holders Required to declare all notes due and payable	25.00%
Senior Notes \| Maximum
Debt Instrument [Line Items]
Debt Instrument, Increase (Decrease) in Interest Rate, Stated Percentage	1.00%
Senior Notes \| Term 1
Debt Instrument [Line Items]
Debt Instrument, Increase (Decrease) in Interest Rate, Stated Percentage	0.25%
Exchange offer not declared effective, term 1	90 days
Senior Notes \| Subsequent Terms
Debt Instrument [Line Items]
Debt Instrument, Increase (Decrease) in Interest Rate, Stated Percentage	0.25%
Exchange offer not declared effective, subsequent terms	90 days
Senior Notes \| Prior to July 1 2016
Debt Instrument [Line Items]
Limit on redemption as a percentage of principal	35.00%
Redemption price as a percentage of principal	107.50%
Senior Notes \| On or After July 1 2016
Debt Instrument [Line Items]
Redemption price as a percentage of principal	105.625%
Senior Notes \| July 1 2019
Debt Instrument [Line Items]
Redemption price as a percentage of principal	100.00%
Finance Corp.
Debt Instrument [Line Items]
Cumulative percentage ownership in subsidiary	100.00%

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Schedule of Units) (Details) - shares			12 Months Ended
	Jun. 21, 2013	Jun. 04, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Partners' Capital Account, Units					0
Common limited partner capital units outstanding, beginning balance			24,412,427
Subordinated limited partner capital units outstanding, begining balance			24,409,850
General partner interests units outstanding, beginning balance			996,320
Partner capital units outstanding, beginning balance			49,818,597.000
Common limited partner capital units outstanding, ending balance			29,079,866	24,412,427
Subordinated limited partner capital units outstanding, ending balance			24,409,850	24,409,850
General partner interests units outstanding, ending balance			1,091,453	996,320
Limited Partners' Capital Account, Units Issued During Period			5,892.000
Partner capital units outstanding, ending balance			54,581,169	49,818,597.000
Common units sold in public offering				14,380,000
Partners' Capital Account, Units, Sold in Private Placement				35,436,020.00
Partners' Capital Account, Units, Unit-based Compensation				2,577.000
Bison Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition			1,585,560.00
Mountaineer Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition			3,171,120.00
Common
Class of Stock [Line Items]
Partners' Capital Account, Units					0
Common limited partner capital units outstanding, beginning balance			24,412,427
Common limited partner capital units outstanding, ending balance			29,079,866	24,412,427
Limited Partners' Capital Account, Units Issued During Period			5,892
Common units sold in public offering				14,380,000
Partners' Capital Account, Units, Sold in Private Placement				10,029,850
Partners' Capital Account, Units, Unit-based Compensation				2,577
Common \| Bison Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition		1,553,849	1,553,849
Common \| Mountaineer Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition	3,107,698		3,107,698
Subordinated
Class of Stock [Line Items]
Partners' Capital Account, Units					0
Subordinated limited partner capital units outstanding, begining balance			24,409,850
Subordinated limited partner capital units outstanding, ending balance			24,409,850	24,409,850
Common units sold in public offering				0
Partners' Capital Account, Units, Sold in Private Placement				24,409,850
Partners' Capital Account, Units, Unit-based Compensation				0
Subordinated \| Bison Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition			0
Subordinated \| Mountaineer Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition			0
General partner
Class of Stock [Line Items]
Partners' Capital Account, Units					0
General partner interests units outstanding, beginning balance			996,320
General partner interests units outstanding, ending balance			1,091,453	996,320
Common units sold in public offering				0
Partners' Capital Account, Units, Sold in Private Placement				996,320
Partners' Capital Account, Units, Unit-based Compensation				0
General partner \| Bison Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition		31,711	31,711
General partner \| Mountaineer Midstream
Class of Stock [Line Items]
Units issued in connection with acquisition	63,422		63,422

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Bison Acquisition) (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Jun. 04, 2013	Jun. 03, 2013	Oct. 03, 2012	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Transaction costs					$ 2,770	$ 2,020	$ 3,166
Net assets in excess of consideration paid	$ 56,535				56,535	$ 0	$ 0
General partner
Business Acquisition [Line Items]
General partner interest (as a percent)	2.00%		2.00%	2.00%
Bison Midstream
Business Acquisition [Line Items]
Cumulative percentage ownership after all transactions	100.00%
Volume weighted average share price, term		5 days
Volume weighted average share price		$ 31.53
Cost of acquired entity, cash paid	$ 200,000
Units issued to acquire entity					$ 200,000
Units issued in connection with acquisition					1,585,560.00
Net assets in excess of consideration paid					$ 0
Closing unit price	$ 30.85
SMP Holdings' net investment in Bison Midstream	$ 305,449
Bison Midstream \| General partner
Business Acquisition [Line Items]
Units issued to acquire entity					(978)
Net assets in excess of consideration paid	1,131				$ 1,131
Limited partners, Common \| Bison Midstream
Business Acquisition [Line Items]
Units issued to acquire entity	$ (47,936)
Units issued in connection with acquisition	1,553,849				1,553,849
General Partner Units \| Bison Midstream
Business Acquisition [Line Items]
Units issued to acquire entity	$ (978)
Units issued in connection with acquisition	31,711				31,711
Limited Partner Common and General Partner Units \| Bison Midstream
Business Acquisition [Line Items]
Units issued to acquire entity	$ (50,000)
SMP Holdings' equity in Bison Midstream \| Bison Midstream
Business Acquisition [Line Items]
Cost of acquired entity, cash paid	200,000
Units issued to acquire entity	$ 248,914				$ 248,914
Net assets in excess of consideration paid					$ (56,535)

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Mountaineer Acquisition) (Details) - Mountaineer Midstream - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jun. 21, 2013	Jun. 03, 2013	Dec. 31, 2013
Business Acquisition [Line Items]
Cost of acquired entity, purchase price	$ 210,000
Cost of acquired entity, cash paid	110,000
Units issued to acquire entity	100,000		$ 100,000
Volume weighted average share price, term		5 days
Volume weighted average share price		$ 31.53
Units issued in connection with acquisition			3,171,120.00
Cost of acquired entity, equity interests issued and issuable	100,000
Limited partners, Common
Business Acquisition [Line Items]
Units issued to acquire entity	$ 98,000		$ 98,000
Units issued in connection with acquisition	3,107,698		3,107,698
General Partner Units
Business Acquisition [Line Items]
Units issued to acquire entity	$ 2,000
Units issued in connection with acquisition	63,422		63,422

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Cash Distributions) (Details) - USD ($)						12 Months Ended
	Feb. 14, 2014	Nov. 14, 2013	Aug. 14, 2013	May 15, 2013	Feb. 14, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Distribution Made to Limited Partner [Line Items]
Per-unit distribution		$ 0.46	$ 0.435	$ 0.42	$ 0.41
Distributions to unitholders		$ 25,108,000	$ 23,740,000	$ 20,923,000	$ 20,425,000	$ 90,196,000	$ 0	$ 0
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Per-unit distribution	$ 0.48
Distributions to unitholders	$ 26,366,000
General partner \| Subsequent Event
Distribution Made to Limited Partner [Line Items]
General partner's IDRs	163,000
Limited partners, Common
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		13,377,000	12,647,000	10,253,000	10,009,000
Limited partners, Common \| Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders	13,958,000
Subordinated
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		11,229,000	10,618,000	10,252,000	10,008,000
Subordinated \| Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders	11,717,000
General Partner Units
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		$ 502,000	$ 475,000	$ 418,000	$ 408,000
General Partner Units \| Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders	$ 691,000

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Subordination and Cash Distribution Policy) (Details) - $ / shares			1 Months Ended	12 Months Ended
	Jun. 04, 2013	Oct. 03, 2012	Mar. 31, 2013	Dec. 31, 2013
Schedule of Partners' Capital [Line Items]
Maximum period following end of quarter to distribute all available cash				45 days
General partner
Schedule of Partners' Capital [Line Items]
General partner interest (as a percent)	2.00%	2.00%	2.00%
Condition one
Schedule of Partners' Capital [Line Items]
Minimum quarterly distribution (in dollars per share)				$ 1.60
Term for condition to be met to end subordination period				3 years
Condition one \| General partner
Schedule of Partners' Capital [Line Items]
General partner interest (as a percent)				2.00%
Condition two
Schedule of Partners' Capital [Line Items]
Minimum quarterly distribution (in dollars per share)				$ 2.40
Percent of minimum distribution				150.00%
Condition two \| General partner
Schedule of Partners' Capital [Line Items]
General partner interest (as a percent)				2.00%
Subordinated units
Schedule of Partners' Capital [Line Items]
Common unit per subordinated unit upon conversion at end of subordination period (in shares)				1

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Minimum Quarterly Distribution) (Details)	12 Months Ended
	Dec. 31, 2013 $ / shares
Equity [Abstract]
Minimum quarterly distributions (in dollars per share)	$ 0.40
Minimum annual distributions (in dollars per share)	$ 1.60

PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Partnership Target Distributions) (Details)	12 Months Ended
	Dec. 31, 2013 $ / shares
Minimum quarterly distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	$ 0.4
Thereafter
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.60
Minimum \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.40
Minimum \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.46
Minimum \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.50
Maximum \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.46
Maximum \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	0.5
Maximum \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount	$ 0.6
Unitholders \| Minimum quarterly distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	98.00%
Unitholders \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	98.00%
Unitholders \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	85.00%
Unitholders \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	75.00%
Unitholders \| Thereafter
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	50.00%
General partner
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	2.00%
Quarterly distributions per unit, incentive threshold	$ 0.46
General partner \| Minimum quarterly distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	2.00%
General partner \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	2.00%
General partner \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	15.00%
General partner \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	25.00%
General partner \| Thereafter
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions	50.00%
General partner \| Maximum
Schedule of Partnership Target Distributions [Line Items]
Percentage interest in distributions in excess of incentive threshold	50.00%

EARNINGS PER UNIT (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 43,636	$ 41,726	$ 37,951
Less: net income attributable to the pre-IPO period	0	24,112
Less: net income attributable to SMP Holdings	52	0
Net income attributable to SMLP	43,584	17,614
Less: net income attributable to general partner, including IDRs	1,035	352
Net income attributable to limited partners	$ 42,549	$ 17,262
Weighted-average common units outstanding – basic (in units)	26,951,346	24,412,427
Less: effect of non-vested phantom units and non-vested restricted units (in units)	150,133	131,558
Weighted-average common units outstanding – diluted (in units)	27,101,479	24,543,985
Weighted-average subordinated units outstanding – basic and diluted (in units)	24,409,850	24,409,850
Earnings per common unit – basic (in dollars per unit)	$ 0.86	$ 0.35
Earnings per common unit – diluted (in dollars per unit)	0.86	0.35
Earnings per subordinated unit – basic and diluted (in dollars per unit)	$ 0.79	$ 0.35
Limited partners, Common
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 22,311	$ 8,631
Net income attributable to limited partners	23,227	8,632
Subordinated units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to limited partners	$ 19,322	$ 8,630

UNIT-BASED COMPENSATION (Narrative) (Details) $ in Thousands	7 Months Ended	12 Months Ended
	Apr. 30, 2013 USD ($) holder shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($) shares	Dec. 31, 2011 USD ($) shares	Dec. 31, 2009	May 01, 2013 shares
Other disclosures
Payment to acquire vested net profit interests \| $		$ 11,957	$ 0	$ 0
Common Units \| Long-term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units reserved for issuance pursuant to LTIP		5,000,000.0
Units available for future issuance		4,700,000
Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Units forfeited (in shares)		4,041
Other disclosures
Nonvested phantom and restricted units (in shares)		283,682	131,558	0
Phantom Units \| Granted in March 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized non-cash compensation expense \| $		$ 3,600
Remaining expected weighted-average vesting period of recognition of incremental non-cash compensation expense		2 years 7 months 31 days
Phantom Units \| Granted in October 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units forfeited (in shares)		0
DFW Net Profits Interests
Other disclosures
Number of holders of net profit interest \| holder	7
Payment to acquire vested net profit interests \| $	$ 12,200
Nonvested phantom and restricted units (in shares)						0
Period of recognition of compensation expense		4 years
Non-cash compensation expense - prior periods (in dollars) \| $			$ 600
Compensation expense due to modification \| $			1,400
SMLP Restricted Units
Other disclosures
Restricted units exchanged for unvested net profit interests	7,393
SMP Net Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		5 years
Other disclosures
Non-cash compensation expense - prior periods (in dollars) \| $			$ 500
Portion of membership interests issued, percent		6.355%
Portion of membership interests forfeited, percent		0.00%
Maximum \| DFW Net Profits Interests
Other disclosures
Portion of membership interests authorized for issuance, percent					5.00%
Maximum \| SMP Net Profits Interests
Other disclosures
Portion of membership interests authorized for issuance, percent					7.50%

UNIT-BASED COMPENSATION (Phantom and Restricted Unit Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Phantom Units
Phantom and Restricted Unit Activity
Nonvested phantom and restricted units, beginning of period (in shares)	131,558	0
Units granted (in shares)	155,330	125,000
Units forfeited (in shares)	(4,041)
Nonvested phantom and restricted units, end of period (in shares)	283,682	131,558
Weighted-average grant date fair value
Nonvested, Weighted-average grant date fair value, beginning	$ 20.00	$ 0.00
Units granted, Weighted-average grant date fair value	26.33	20.00
Units forfeited, Weighted-average grant date fair value	25.99
Nonvested, Weighted-average grant date fair value, ending	$ 23.41	$ 20.00
Restricted Units
Phantom and Restricted Unit Activity
Units granted (in shares)	835	6,558
Weighted-average grant date fair value
Units granted, Weighted-average grant date fair value	$ 27.50	$ 20.23

UNIT-BASED COMPENSATION (Unit-based Compensation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Long-term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation	$ 2,999	$ 269	$ 0

UNIT-BASED COMPENSATION (Inputs Used in Option Pricing Method) (Details)	1 Months Ended
	Jan. 31, 2012	Oct. 31, 2011	Apr. 30, 2011	Jul. 31, 2010	Apr. 30, 2010	Sep. 30, 2009
DFW Net Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Length of holding period restriction				3 years 5 months 5 days	3 years 9 months	4 years 3 months
Discount for lack of marketability (as a percent)				35.90%	30.90%	34.80%
Volatility (as a percent)				53.70%	49.80%	52.50%
SMP Net Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Length of holding period restriction	2 years 11 months 5 days	3 years 2 months 16 days	4 years 9 months		3 years 9 months	4 years 3 months
Discount for lack of marketability (as a percent)	24.00%	33.10%	29.60%		30.90%	34.80%
Volatility (as a percent)	37.00%	49.30%	43.20%		49.80%	52.50%

UNIT-BASED COMPENSATION (Amount and Grant-date Fair Value of Vested and Nonvested Interests) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
DFW Net Profits Interests
Percentage Interest
Nonvested at the beginning of the period (as a percent)	0.038%	1.75%	2.85%
Repurchased (as a percent)	0.038%	0.00%	0.00%
Granted (as a percent)	0.00%	0.00%	0.00%
Vested (as a percent)	0.00%	1.644%	1.10%
Forfeited (as a percent)	0.00%	0.069%	0.40%
Nonvested at the end of the period (as a percent)	0.00%	0.038%	1.75%
Vested at the end of the period (as a percent)	0.00%	4.294%	2.65%
Weighted-average grant date Fair Value (per 1.0% of SMP Net Profits Interest)
Nonvested at the beginning of the period (in dollars)	$ 1,650	$ 306	$ 295
Repurchased (in dollars)	1,650	0	0
Granted (in dollars)	0	0	0
Vested (in dollars)	0	256	277
Forfeited (in dollars)	0	765	220
Vested at the end of the period (in dollars)	0	257	258
Nonvested at the end of the period (in dollars)	$ 0	$ 1,650	$ 306
SMP Net Profits Interests
Percentage Interest
Nonvested at the beginning of the period (as a percent)	3.958%	2.944%
Granted (as a percent)	0.50%	2.00%
Vested (as a percent)	1.271%	0.986%
Nonvested at the end of the period (as a percent)	3.187%	3.958%	2.944%
Vested at the end of the period (as a percent)	3.168%	1.897%
Weighted-average grant date Fair Value (per 1.0% of SMP Net Profits Interest)
Nonvested at the beginning of the period (in dollars)	$ 1,003	$ 601
Granted (in dollars)	1,780	1,505
Vested (in dollars)	965	818
Vested at the end of the period (in dollars)	788	669
Nonvested at the end of the period (in dollars)	$ 1,140	$ 1,003	$ 601

UNIT-BASED COMPENSATION (Non-cash Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
DFW Net Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash compensation expense (in dollars)	$ 17	$ 688	$ 2,171
SMP Net Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash compensation expense (in dollars)	$ 919	$ 1,269

CONCENTRATIONS OF RISK (Details)	12 Months Ended
CONCENTRATIONS OF RISK (Details)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Counterparty A \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage	22.00%	28.00%
Counterparty A \| Accounts receivable \| Credit concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage	44.00%	38.00%
Counterparty B \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage	18.00%	20.00%	34.00%
Counterparty B \| Accounts receivable \| Credit concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage	13.00%	24.00%
Counterparty C \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage		12.00%	17.00%
Counterparty C \| Accounts receivable \| Credit concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage	0.00%
Counterparty D \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage			12.00%
Counterparty E \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Total revenues, major customer percentage			10.00%

RELATED-PARTY TRANSACTIONS (Details) - USD ($)		1 Months Ended		12 Months Ended
RELATED-PARTY TRANSACTIONS (Details) - USD ($)	Oct. 27, 2011	Jul. 31, 2012	May 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
RELATED-PARTY TRANSACTIONS
Due to affiliate				$ 653,000	$ 0
Due from affiliate				0	774,000
Interest paid in kind				0	5,426,000	$ 2,025,000
General partner
RELATED-PARTY TRANSACTIONS
Due to affiliate				653,000	0
Due from affiliate				0	774,000
General and administrative expense allocation				3,914,000	1,200,000	0
Equipower
RELATED-PARTY TRANSACTIONS
Payments for electricity management consulting services				199,000	204,000	$ 11,000
IPS Engineering/EPC
RELATED-PARTY TRANSACTIONS
Payments for electricity management consulting services				200,000
Sponsors
RELATED-PARTY TRANSACTIONS
Transaction expenses receivable					$ 1,300,000
Reimbursements received for transaction expenses				300,000
Write-off of transaction expense receivable				1,000,000
Notes Payable \| Sponsors
RELATED-PARTY TRANSACTIONS
Notes	$ 200,000,000.0
Interest rate (as a percent)	8.00%
Prepayment of notes		$ 49,200,000	$ 160,000,000
Interest paid in kind				6,300,000
Interest expense capitalized related to costs incurred on capital projects under construction				$ 900,000
Revolving credit facility
RELATED-PARTY TRANSACTIONS
Additional borrowings		$ 50,000,000	$ 163,000,000

BENEFIT PLAN (Details) - USD ($) $ in Millions	12 Months Ended
BENEFIT PLAN (Details) - USD ($) $ in Millions	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation and Retirement Disclosure [Abstract]
Defined contribution benefit plan expense	$ 0.4	$ 0.2	$ 0.1

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments and Contingencies Disclosure [Abstract]
Total rent expense related to operating leases	$ 1,127	$ 724	$ 489
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2014	1,032
2015	1,013
2016	974
2017	707
2018	$ 522

ACQUISITIONS (Bison Midstream) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 04, 2013	Dec. 31, 2013	Feb. 15, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 115,888		$ 45,478	$ 45,478
Gas Gathering Contract \| Minimum
Business Acquisition [Line Items]
Useful lives		10 years
Gas Gathering Contract \| Maximum
Business Acquisition [Line Items]
Useful lives		25 years
Bison Midstream
Business Acquisition [Line Items]
Cost of acquired entity, purchase price	$ 248,900
Cost of acquired entity, cash paid	200,000
Purchase price assigned to Bison Gas Gathering system		$ 303,168
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Purchase price assigned to Bison Gas Gathering system			$ 303,168
Current assets			5,705
Property, plant, and equipment			85,477
Intangible assets			164,502
Other noncurrent assets			2,187
Total assets acquired			257,871
Current liabilities			6,112
Other noncurrent liabilities			2,790
Total liabilities assumed			8,902
Net identifiable assets acquired			248,969
Goodwill		54,200	$ 54,199
Bison Midstream \| Limited partners, Common
Business Acquisition [Line Items]
Cost of acquired entity, equity interests issued and issuable	47,900
Bison Midstream \| General Partner Units
Business Acquisition [Line Items]
Cost of acquired entity, equity interests issued and issuable	1,000
Bison Midstream \| SMP Holdings' equity in Bison Midstream
Business Acquisition [Line Items]
Cost of acquired entity, purchase price	248,900
Cost of acquired entity, cash paid	200,000
Purchase price assigned to Bison Gas Gathering system	$ 303,200	$ 303,168
Bison Midstream \| Weighted Average
Business Acquisition [Line Items]
Useful lives	12 years
Bison Midstream \| Gas Gathering Contract \| Minimum
Business Acquisition [Line Items]
Useful lives	5 years
Bison Midstream \| Gas Gathering Contract \| Maximum
Business Acquisition [Line Items]
Useful lives	15 years

ACQUISITIONS (Revenue and Net Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Revenues	$ 242,806	$ 165,499	$ 103,552
Net income	43,636	$ 41,726	$ 37,951
Summit Midstream Partners, LP
Business Acquisition [Line Items]
Revenues	225,192
Net income	43,584
Bison Midstream, LLC
Business Acquisition [Line Items]
Revenues	17,614
Net income	$ 52

ACQUISITIONS (Mountaineer Midstream) (Details) $ in Thousands		12 Months Ended
	Jun. 21, 2013 USD ($) compressor_station	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 115,888	$ 45,478	$ 45,478
Contract intangibles
Business Acquisition [Line Items]
Useful lives		12 years 6 months	12 years 4 months 24 days
Rights-of-way
Business Acquisition [Line Items]
Useful lives		28 years 3 months 18 days	28 years 3 months 18 days
Mountaineer Midstream
Business Acquisition [Line Items]
Cost of acquired entity, purchase price	$ 210,000
Number of compressor stations acquired \| compressor_station	2
Cost of acquired entity, cash paid	$ 110,000
Cost of acquired entity, equity interests issued and issuable	100,000
Mountaineer Midstream revenues since acquisition		$ 9,600
Mountaineer Midstream net income since acquisition		$ 2,300
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Purchase price	210,000
Property, plant, and equipment	163,661
Total assets acquired	193,789
Total liabilities assumed	0
Net identifiable assets acquired	193,789
Goodwill	16,211
Mountaineer Midstream \| Gas gathering agreement contract intangibles
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangible assets	24,019
Mountaineer Midstream \| Rights-of-way
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangible assets	$ 6,109
Weighted Average \| Mountaineer Midstream
Business Acquisition [Line Items]
Useful lives	13 years
Scenario, Previously Reported \| Mountaineer Midstream
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Property, plant, and equipment	$ 158,300
Goodwill	18,100
Scenario, Previously Reported \| Mountaineer Midstream \| Contract intangibles
Business Acquisition [Line Items]
Purchase price assigned, intangibles assets	27,100
Scenario, Previously Reported \| Mountaineer Midstream \| Rights-of-way
Business Acquisition [Line Items]
Purchase price assigned, intangibles assets	$ 6,500

ACQUISITIONS (Pro Forma) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma total revenues	$ 254,957	$ 203,093	$ 167,671
Pro forma net income	$ 40,661	$ 32,167	54,405
Limited partners, Common
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma EPU, basic and diluted	$ 0.74	$ 0.29
Subordinated units
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma EPU, basic and diluted	$ 0.74	$ 0.29
Acquisition-related Costs
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma effect of nonrecurring transaction costs incurred on net income	$ 2,500
Bison Midstream and Mountaineer Midstream
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Incremental borrowings on revolving credit facility	310,000
Pro forma total revenues	60,323	$ 0
Pro forma net income	$ (457)	$ 0
Grand River Gathering, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma total revenues			12,824
Pro forma net income			$ 2,660

ACQUISITIONS (Grand River Gathering) (Details) $ in Thousands		12 Months Ended
	Oct. 27, 2011 USD ($) mi hp	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Jun. 30, 2012 USD ($)
Business Acquisition [Line Items]
Equity contribution		$ 0	$ 0	$ 425,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 115,888	$ 45,478	45,478
Grand River Gathering, LLC
Business Acquisition [Line Items]
Length of pipeline acquired (in miles) \| mi	260
Capacity of compression facilities acquired (in horsepower) \| hp	90,000
Equity contribution	$ 410,000
Nonrecurring transaction costs				3,200
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Purchase price	590,210
Property, plant, and equipment	295,240
Total assets acquired	547,356
Deferred revenue	1,770
Other current liabilities	854
Total liabilities assumed	2,624
Net identifiable assets acquired	544,732
Goodwill	$ 45,478			$ 45,500
Minimum \| Grand River Gathering, LLC
Business Acquisition [Line Items]
Useful lives	10 years
Maximum \| Grand River Gathering, LLC
Business Acquisition [Line Items]
Useful lives	25 years
Weighted Average \| Grand River Gathering, LLC
Business Acquisition [Line Items]
Useful lives	12 years 9 months
Sponsors \| Grand River Gathering, LLC
Business Acquisition [Line Items]
Proceeds from promissory notes	$ 200,000
Gas gathering agreement contract intangibles \| Grand River Gathering, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangible assets	244,100
Rights-of-way \| Grand River Gathering, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangible assets	$ 8,016
Purchase Price Allocation Adjustments \| Grand River Gathering, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Intangible assets					$ (37,900)
Construction in progress \| Purchase Price Allocation Adjustments \| Grand River Gathering, LLC
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Property, plant, and equipment					$ (4,700)

SUBSQUENT EVENT (Details) - Red Rock Gathering Company, LLC - Subsequent Event $ in Millions	Mar. 08, 2014 USD ($)
Subsequent Event [Line Items]
Percentage of interests acquired	100.00%
Cost of acquired entity, cash paid	$ 305.0

Label	Element	Value
Bison Midstream [Member] \| Limited Partner Common [Member]
Partners' Capital Account, Net Assets in Excess of Consideration Paid	smlp_PartnersCapitalAccountNetAssetsinExcessofConsiderationPaid	$ 28,558,000
Bison Midstream [Member] \| Limited Partner Subordinated [Member]
Partners' Capital Account, Net Assets in Excess of Consideration Paid	smlp_PartnersCapitalAccountNetAssetsinExcessofConsiderationPaid	$ 26,846,000