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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2014	Jul. 31, 2014
Entity Registrant Name	Summit Midstream Partners, LP
Entity Central Index Key	0001549922
Document Type	10-Q
Document Period End Date	Jun. 30, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q2
Common units
Entity Common Stock, Shares Outstanding		34,423,369
Subordinated Units
Entity Common Stock, Shares Outstanding		24,409,850
General Partner Units
Entity Common Stock, Shares Outstanding		1,200,651

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 23,430	$ 20,357
Accounts receivable	53,345	67,877
Other assets	2,044	4,741
Total current assets	78,819	92,975
Property, plant and equipment, net	1,198,727	1,158,081
Intangible assets, net:
Favorable gas gathering contracts	17,010	17,880
Contract intangibles	367,146	383,306
Rights-of-way	101,923	100,991
Total intangible assets, net	486,079	502,177
Goodwill	115,888	115,888
Other noncurrent assets	13,621	14,618
Total assets	1,893,134	1,883,739
Current liabilities:
Trade accounts payable	29,670	25,117
Due to affiliate	1,578	653
Deferred revenue	2,609	1,555
Ad valorem taxes payable	6,883	8,375
Accrued interest	11,250	12,144
Other current liabilities	9,943	11,729
Total current liabilities	61,933	59,573
Long-term debt	726,000	586,000
Noncurrent liability, net	5,955	6,374
Deferred revenue	37,093	29,683
Other noncurrent liabilities	1,597	372
Total liabilities	832,578	682,002
Commitments and contingencies
Common limited partner capital (34,423,369 units issued and outstanding at June 30, 2014 and 29,079,866 units issued and outstanding at December 31, 2013)	702,298	566,532
Subordinated limited partner capital (24,409,850 units issued and outstanding at June 30, 2014 and December 31, 2013)	332,389	379,287
General partner interests (1,200,651 units issued and outstanding at June 30, 2014 and 1,091,453 issued and outstanding at December 31, 2013)	25,869	23,324
Summit Investments' equity in contributed subsidiaries	0	232,594
Total partners' capital	1,060,556	1,201,737
Total liabilities and partners' capital	$ 1,893,134	$ 1,883,739

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Jun. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Common limited partner capital, units issued	34,423,369	29,079,866
Common limited partner capital, units outstanding	34,423,369	29,079,866
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	1,200,651	1,091,453
General partner interests, units outstanding	1,200,651	1,091,453

UNAUDITED CONDESNED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues:
Gathering services and other fees	$ 54,831	$ 47,914	$ 104,903	$ 93,888
Natural gas, NGLs and condensate sales and other	26,190	23,797	52,546	40,088
Amortization of favorable and unfavorable contracts	(225)	(250)	(451)	(530)
Total revenues	80,796	71,461	156,998	133,446
Costs and expenses:
Cost of natural gas and NGLs	16,378	13,438	31,660	21,403
Operation and maintenance	19,859	18,371	39,040	35,950
General and administrative	8,690	8,406	16,576	14,973
Transaction costs	76	2,435	612	2,473
Depreciation and amortization	20,480	16,801	40,122	30,714
Total costs and expenses	65,483	59,451	128,010	105,513
Other (expense) income	(5)	1	(4)	2
Interest expense	(10,803)	(3,023)	(17,947)	(4,903)
Income before income taxes	4,505	8,988	11,037	23,032
Income tax expense	(469)	(221)	(628)	(402)
Net income	4,036	8,767	10,409	22,630
Less: net income attributable to Summit Investments (Note 1)	0	699	2,828	2,082
Net income attributable to SMLP	4,036	8,068	7,581	20,548
Less: net income attributable to general partner, including IDRs	801	161	1,232	411
Net income attributable to limited partners	$ 3,235	$ 7,907	$ 6,349	$ 20,137
Weighted-average limited partner units outstanding
Cash distributions declared per common unit (in dollars per unit)	$ 0.5	$ 0.42	$ 0.98	$ 0.83
Common units
Costs and expenses:
Net income attributable to limited partners	$ 1,891	$ 4,012	$ 4,398	$ 10,127
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Weighted-average limited partner units outstanding
Basic (shares)	34,422,273	25,172,087	32,179,431	24,790,158
Diluted (shares)	34,618,506	25,281,104	32,360,022	24,871,033
Subordinated Units
Costs and expenses:
Net income attributable to limited partners	$ 1,344	$ 3,895	$ 1,951	$ 10,010
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41
Weighted-average limited partner units outstanding
Basic (shares)	24,409,850	24,409,850	24,409,850	24,409,850
Diluted (shares)	24,409,850	24,409,850	24,409,850	24,409,850

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	SMLP units	Class B Units	Summit Investments' equity in contributed subsidiaries	Summit Investments' equity in contributed subsidiaries Class B Units	Limited partners, Common	Limited partners, Common SMLP units	Limited partners, Common Class B Units	Limited partners, Subordinated	General partner	Bison Midstream	Bison Midstream Summit Investments' equity in contributed subsidiaries	Bison Midstream Limited partners, Common	Bison Midstream Limited partners, Subordinated	Bison Midstream General partner	Mountaineer Midstream	Mountaineer Midstream Limited partners, Common	Mountaineer Midstream General partner
Beginning balance at Dec. 31, 2012	$ 1,030,248			$ 211,001		$ 418,856			$ 380,169	$ 20,222
Members Interest Increase (Decrease) [Roll Forward]
Net income	22,630			2,082		10,127			10,010	411
Unit-based compensation		$ 1,141	$ 261		$ 244		$ 1,141	$ 17
Consolidation of Bison Midstream net assets	303,168			303,168
Contribution from Summit Investments to Bison Midstream											$ 2,229	$ 2,229
Units issued to acquire entity											(200,000)	(248,914)	$ 47,936		$ 978	$ 100,000	$ 98,000	$ 2,000
Contribution of net assets from Summit Investments in excess of consideration paid for Bison Midstream	56,535										$ 0	$ (56,535)	$ 28,558	$ 26,846	$ 1,131
Cash advance from Summit Investments to contributed subsidiaries	(2,243)			(2,243)
Expense paid by Summit Investments	4,762			4,762
Partners' Capital Account, Capitalized Interest Allocated To Affiliates	109			109
Distributions to unitholders	(41,348)					(20,262)			(20,260)	(826)
Repurchase of DFW Net Profit Interests	(11,957)					(5,859)			(5,859)	(239)
Ending balance at Jun. 30, 2013	1,209,000			215,903		578,514			390,906	23,677
Beginning balance at Dec. 31, 2013	1,201,737			232,594		566,532			379,287	23,324
Members Interest Increase (Decrease) [Roll Forward]
Net income	10,409			2,828		3,634			2,715	1,232
Unit-based compensation	2,424					2,424
Tax withholdings on vested SMLP LTIP awards	(656)					(656)
Issuance of common units, net of offering costs	197,989					197,989
Contribution from general partner	4,235									4,235
Contribution of net assets from Summit Investments in excess of consideration paid for Bison Midstream	0
Purchase of Red Rock Gathering	(305,000)			(305,000)
Excess of purchase price over acquired carrying value of Red Rock Gathering	0			63,183		(36,228)			(25,691)	(1,264)
Cash advance from Summit Investments to contributed subsidiaries	1,982			1,982
Expense paid by Summit Investments	4,413			4,413
Repurchase of SMLP LTIP units		$ (228)					$ (228)
Distributions to unitholders	(56,749)					(31,169)			(23,922)	(1,658)
Ending balance at Jun. 30, 2014	$ 1,060,556			$ 0		$ 702,298			$ 332,389	$ 25,869

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 10,409	$ 22,630
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	40,573	31,244
Amortization of deferred loan costs	1,220	882
Unit-based compensation	2,424	1,402
Loss on asset sales	6	0
Changes in operating assets and liabilities:
Accounts receivable	14,532	(434)
Due to affiliate	925	2,674
Trade accounts payable	2,319	2,525
Change in deferred revenue	8,464	5,695
Ad valorem taxes payable	(1,492)	(2,200)
Accrued interest	(894)	(16)
Other, net	2,213	5,070
Net cash provided by operating activities	80,699	69,472
Cash flows from investing activities:
Capital expenditures	(63,336)	(49,642)
Proceeds from asset sales	24	0
Acquisition of gathering system from third party	0	(210,000)
Acquisition of gathering system from affiliate	(305,000)	(200,000)
Net cash used in investing activities	(368,312)	(459,642)
Cash flows from financing activities:
Distributions to unitholders	(56,749)	(41,348)
Borrowings under revolving credit facility	160,000	360,000
Repayments under revolving credit facility	(20,000)	(294,180)
Deferred loan costs	(300)	(7,333)
Tax withholdings on vested SMLP LTIP awards	(656)	0
Proceeds from issuance of common units, net	197,989	0
Contribution from general partner	4,235	0
Cash advance from (to) Summit Investments to (from) contributed subsidiaries, net	1,982	(11)
Expenses paid by Summit Investments on behalf of contributed subsidiaries	4,413	5,117
Issuance of 7.5% senior notes	0	300,000
Issuance of units to affiliate in connection with the Mountaineer Acquisition	0	100,000
Repurchase of equity-based compensation awards	(228)	(11,957)
Net cash provided by financing activities	290,686	410,288
Net change in cash and cash equivalents	3,073	20,118
Cash and cash equivalents, beginning of period	20,357	11,334
Cash and cash equivalents, end of period	23,430	31,452
Supplemental Cash Flow Disclosures:
Cash interest paid	17,153	4,014
Less: capitalized interest	3,688	1,559
Interest paid (net of capitalized interest)	13,465	2,455
Cash paid for taxes	0	660
Noncash Investing and Financing Activities:
Capital expenditures in trade accounts payable (period-end accruals)	18,703	6,680
Excess of purchase price over acquired carrying value of Red Rock Gathering	63,183	0
Issuance of units to affiliate to partially fund the Bison Drop Down	0	48,914
Contribution of net assets from Summit Investments in excess of consideration paid for Bison Midstream	$ 0	$ 56,535

ORGANIZATION, BUSINESS OPERATIONS AND BASIS OF PRESENTATION

6 Months Ended

Jun. 30, 2014

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 had a 100% ownership interest in Summit Midstream Holdings, LLC ("Summit Holdings") which had a 100% ownership interest in both DFW Midstream Services LLC ("DFW Midstream") and Grand River Gathering, LLC ("Grand River Gathering").

On June 4, 2013, the Partnership acquired all of the membership interests of Bison Midstream, LLC ("Bison Midstream") from a wholly owned 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"), which was subsequently renamed Meadowlark Midstream Company, LLC ("Meadowlark Midstream"). The Bison Gas Gathering system was carved out from Meadowlark Midstream in connection with the Bison Drop Down. As such, it was deemed a transaction among entities under common control.

On June 21, 2013, Mountaineer Midstream Company, LLC ("Mountaineer Midstream"), a newly formed, wholly owned subsidiary of the Partnership, acquired certain natural gas gathering pipeline and compression assets in the Marcellus Shale Play in Doddridge and Harrison counties, West Virginia from an affiliate of MarkWest Energy Partners, L.P. ("MarkWest") (the "Mountaineer Acquisition").

In October 2012, Summit Investments acquired ETC Canyon Pipeline, LLC ("Canyon") from a subsidiary of Energy Transfer Partners, L.P. The Canyon gathering and processing assets were contributed to Red Rock Gathering Company, LLC ("Red Rock Gathering"), a newly formed, wholly owned subsidiary of Summit Investments. Red Rock Gathering gathers and processes natural gas and natural gas liquids in the Piceance Basin in western Colorado and eastern Utah. On March 18, 2014, SMLP acquired all of the membership interests of Red Rock Gathering from a subsidiary of Summit Investments (the "Red Rock Drop Down"). Concurrent with the closing of the Red Rock Drop Down, SMLP contributed its interest in Red Rock Gathering to Grand River Gathering. For additional information, see Notes 6 and 12.

Summit Investments is a Delaware limited liability company and the predecessor for accounting purposes 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"). On June 17, 2014, GE Energy Financial Services exchanged 100% of its Class A membership interests in Summit Investments for a new class of membership interests, structured as Class C Preferred interests. As a result, GE Energy Financial Services is no longer a Class A member of Summit Investments. Consequently, we refer to Energy Capital Partners and GE Energy Financial Services as our "Sponsors" for the period from August 2011 until June 17, 2014, and we refer to Energy Capital Partners as our sole "Sponsor" subsequent to June 17, 2014. As of June 30, 2014, Summit Investments, through a wholly owned subsidiary, held 9,641,397 SMLP common units, 24,409,850 SMLP subordinated units and 1,200,651 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 have 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.

Business Operations. We provide natural gas gathering, treating and processing services pursuant to primarily long-term and fee-based, natural gas gathering agreements with our customers. Our results are driven primarily by the volumes of natural gas that we gather, treat and process across our systems. Our gathering and processing systems and the unconventional resource basins in which they operate as of June 30, 2014 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 and eastern Utah.

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 and processing systems.

Basis of Presentation and Principles of Consolidation. We prepare our unaudited condensed 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.

These unaudited condensed consolidated financial statements reflect the results of operations of: (i) Red Rock Gathering for all periods presented, (ii) Bison Midstream since February 16, 2013, and (iii) Mountaineer Midstream since June 22, 2013. SMLP recognized its acquisitions of Red Rock Gathering and Bison Midstream at Summit Investments' historical cost because the acquisitions were executed by entities under common control. The excess of the purchase price paid by SMLP over Summit Investments' net investment in Red Rock Gathering was recognized as a reduction to partners' capital. The excess of Summit Investments' 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 Red Rock Drop Down and the Bison Drop Down were accounted for by the Partnership on an “as-if pooled” basis for the periods during which common control existed. The unaudited condensed consolidated financial statements include the assets, liabilities, and results of operations of SMLP and its respective wholly owned subsidiaries. All intercompany transactions among the consolidated entities have been eliminated in consolidation.

These unaudited condensed consolidated financial statements have been prepared pursuant to the rules and the regulations of the Securities and Exchange Commission (the "SEC"). Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations, although the Partnership believes that the disclosures made are adequate to make the information not misleading. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto that are included in our annual report on Form 10-K for the year ended December 31, 2013, as updated and superseded by our current report on Form 8-K dated July 3, 2014 (the "2013 Annual Report"). The results of operations for an interim period are not necessarily indicative of results expected for a full year.

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 and processing 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.

For additional information, see Note 1 to the audited consolidated financial statements included in the 2013 Annual Report.

- Definition

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

+ References

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+ Details

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

6 Months Ended

Jun. 30, 2014

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Other Assets. Other assets primarily consist of prepaid expenses that are charged to expense over the period of benefit or the life of the related contract.

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

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



	June 30, 2014				December 31, 2013
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	426,000	$	426,000	$	286,000	$	286,000
7.5% Senior notes	300,000		326,500		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 June 30, 2014 and 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, treating and processing 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 fee-based gathering, treating and processing 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 and keep-whole 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 substantially all of 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 more 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, treating, and/or processing. 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, process the natural gas and/or 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. The margins earned are directly related to the volume of natural gas that flows through the system and the price at which we are able to sell the residue natural gas and NGLs.

•

Keep-Whole. Under keep-whole arrangements, after processing we keep 100% of the NGLs produced, and the processed natural gas, or value of the natural gas, is returned to the producer. Since some of the natural gas is used and removed during processing, we compensate the producer for the amount of natural gas used and removed in processing by supplying additional natural gas or by paying an agreed-upon value for the natural gas utilized. These arrangements have commodity price exposure for us because the costs are dependent on the price of natural gas and the revenues are based on the price of NGLs.

Certain of our natural gas gathering or processing agreements provide for a monthly, quarterly or annual minimum volume commitment ("MVC") from certain of our customers. Under these 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 period if its actual throughput volumes are less than its MVC for that period. 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.

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 or processing 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 or processing 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.



	Six months ended June 30, 2014
	Current		Noncurrent
	(In thousands)
Deferred revenue, beginning of period	$	1,555	$	29,683
Additions	2,609		7,410
Less: revenue recognized due to expiration	1,555		—
Deferred revenue, end of period	$	2,609	$	37,093

As of June 30, 2014, accounts receivable included $4.8 million of shortfall billings related to MVC arrangements that can be utilized to offset gathering fees in subsequent periods. Noncurrent deferred revenue at June 30, 2014 represents amounts that provide certain customers the ability to offset their gathering fees over a period up to seven years to the extent that the customer's throughput volumes exceeds its MVC.

Income Taxes. Since we are structured as a partnership, we are generally not subject to federal and state income taxes, except as noted below. 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 a 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.

In June 2014, the Company elected to apply changes to the determination of cost of goods sold for the Texas Margin Tax which permits the use of accelerated depreciation allowed for federal income tax purposes. As a result of this change, current income tax expense for the three and six months ended June 30, 2014 was reduced and a deferred tax liability was recognized. The associated deferred tax liability of $1.2 million is included in other noncurrent liabilities at June 30, 2014.

Earnings Per Unit ("EPU"). 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 quarter-to-date and year-to-date periods in 2014 and 2013. 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 June 30, 2014 or December 31, 2013. 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.

Other Significant Accounting Policies. For information on our other significant accounting policies, see Note 2 of the audited consolidated financial statements included in the 2013 Annual Report.

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, except as noted below.

In May 2014, the Financial Accounting Standards Board released a joint revenue recognition standard, Accounting Standards Update No. 2014-09 ("ASC Update 2014-09"). Under ASC Update 2014-09, revenue will be recognized under a five-step model: (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to performance obligations; and (v) recognize revenue when (or as) the partnership satisfies a performance obligation. This new standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016, and interim and annual periods thereafter. Early adoption is not permitted. We are currently in the process of evaluating the impact of this update.

PROPERTY, PLANT, AND EQUIPMENT, NET

6 Months Ended

Jun. 30, 2014

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT, AND EQUIPMENT, NET

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



	Useful lives (In years)	June 30,		December 31,
	Useful lives (In years)	2014		2013
	(Dollars in thousands)
Natural gas gathering and processing systems	30	$	810,617	$	744,359
Compressor stations and compression equipment	30	393,483		380,000
Construction in progress	n/a	63,419		83,765
Other	4-15	24,175		21,304
Total		1,291,694		1,229,428
Less: accumulated depreciation		92,967		71,347
Property, plant, and equipment, net		$	1,198,727	$	1,158,081

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Depreciation expense	$	11,104	$	8,508	$	21,625	$	16,325
Capitalized interest	2,329		1,066		3,688		1,559

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL

6 Months Ended

Jun. 30, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

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:



	June 30, 2014
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(7,185	)	$	17,010
Contract intangibles	12.5	426,464		(59,318		)	367,146
Rights-of-way	24.2	111,975		(10,052		)	101,923
Total amortizable intangible assets		$	562,634	$	(76,555	)	$	486,079

Unfavorable gas gathering contract	10.0	$	10,962	$	(5,007	)	$	5,955



	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	24.3	108,706		(7,715		)	100,991
Total amortizable intangible assets		$	559,365	$	(57,188	)	$	502,177

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

We recognized amortization expense in revenues as follows:



	Three months ended June 30,						Six months ended June 30,
	2014			2013			2014			2013
	(In thousands)
Amortization expense – favorable gas gathering contracts	$	(436	)	$	(527	)	$	(870	)	$	(1,099	)
Amortization expense – unfavorable gas gathering contract	211			277			419			569
Amortization of favorable and unfavorable contracts	$	(225	)	$	(250	)	$	(451	)	$	(530	)

We recognized amortization expense in costs and expenses as follows:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Amortization expense – contract intangibles	$	8,198	$	7,421	$	16,160	$	12,709
Amortization expense – rights-of-way	1,178		872		2,337		1,680

The estimated aggregate annual amortization of intangible assets and noncurrent liability expected to be recognized for the remainder of 2014 and each of the four succeeding fiscal years follows.



	Assets		Liability
	(In thousands)
2014	$	20,589	$	806
2015	43,872		1,650
2016	44,114		1,571
2017	42,846		1,438
2018	43,115		490

Goodwill. 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. There have been no impairments of goodwill.

- 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

6 Months Ended

Jun. 30, 2014

Debt Disclosure [Abstract]

LONG-TERM DEBT

Long-term debt consisted of the following:



	June 30,		December 31,
	2014		2013
	(In thousands)
Variable rate senior secured revolving credit facility (2.40% at June 30, 2014 and 2.42% at December 31, 2013) due November 2018	$	426,000	$	286,000
7.50% Senior unsecured notes due July 2021	300,000		300,000
Total long-term debt	$	726,000	$	586,000

Revolving Credit Facility. We have a variable rate senior secured revolving credit facility (the "revolving credit facility") which allows for revolving loans, letters of credit and swingline loans. 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 (other than Summit Midstream Finance Corp. ("Finance Corp.")).

Borrowings under the revolving credit facility bear interest at the London Interbank Offered Rate ("LIBOR") or an Alternate Base Rate ("ABR") plus an applicable margin, as defined in the credit agreement. At June 30, 2014, the applicable margin under LIBOR borrowings was 2.25%, the interest rate was 2.40% and the unused portion of the revolving credit facility totaled $274.0 million (subject to a commitment fee of 0.375%).

As of June 30, 2014, we were in compliance with the covenants in the revolving credit facility. There were no defaults or events of default during the six months ended June 30, 2014.

Senior Notes. In June 2013, Summit Holdings and its 100% owned finance subsidiary, Finance Corp. (together with Summit Holdings, the "Co-Issuers"), co-issued $300.0 million of 7.50% senior unsecured notes maturing July 1, 2021 (the "7.5% senior notes").

We pay interest on the 7.5% senior notes semi-annually in cash in arrears on January 1 and July 1 of each year. The 7.5% senior notes are senior, unsecured obligations and rank equally in right of payment with all of our existing and future senior obligations. The 7.5% senior notes are effectively subordinated in right of payment to all of our secured indebtedness, to the extent of the collateral securing such indebtedness.

Effective as of April 7, 2014, all of the holders of our 7.5% senior notes exchanged their unregistered senior notes and the guarantees of those notes for registered notes and guarantees. 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.

As of June 30, 2014, we were in compliance with the covenants for the 7.5% senior notes. There were no defaults or events of default during the six months ended June 30, 2014.

On July 15, 2014, Summit Holdings and Finance Corp. co-issued $300.0 million of 5.50% senior unsecured notes maturing August 15, 2022 (the "5.5% senior notes").

We will pay interest on the 5.5% senior notes semi-annually in cash in arrears on February 15 and August 15 of each year, commencing February 15, 2015. The 5.5% senior notes are senior, unsecured obligations and rank equally in right of payment with all of our existing and future senior obligations. The 5.5% 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 5.5% senior notes to repay a portion of the balance outstanding under our revolving credit facility.

At any time prior to August 15, 2017, the Co-Issuers may redeem up to 35% of the aggregate principal amount of the 5.5% senior notes at a redemption price of 105.500% of the principal amount of the 5.5% 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 August 15, 2017, the Co-Issuers may redeem all or part of the 5.5% senior notes at a redemption price of 104.125% (with the redemption premium declining ratably each year to 100.000% on August 15, 2020), plus accrued and unpaid interest, if any.

The 5.5% senior notes' 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 5.5% senior notes' 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 5.5% senior notes; (ii) default in the payment when due of the principal of, or premium, if any, on the 5.5% 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 5.5% 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 5.5% senior notes may declare all the 5.5% senior notes to be due and payable immediately.

SMLP and all of its subsidiaries other than the Co-Issuers (the "Guarantors") have fully and unconditionally and jointly and severally guaranteed the 7.5% senior notes and the 5.5% 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, the 7.5% senior notes and the 5.5% 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 7.5% senior notes and the 5.5% 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.

PARTNERS' CAPITAL

6 Months Ended

Jun. 30, 2014

Equity [Abstract]

PARTNERS' CAPITAL

Partners' Capital

In March 2014, we completed an underwritten public offering of 10,350,000 common units at a price of $38.75 per unit (the "March 2014 Equity Offering"), of which 5,300,000 common units were offered by the Partnership and 5,050,000 common units were offered by an affiliate of Summit Investments, pursuant to an effective shelf registration statement on Form S-3 previously filed with the SEC. Concurrent with the March 2014 Equity Offering, our general partner made a capital contribution to maintain its 2% general partner interest in SMLP. We used the proceeds from the primary offering and the general partner capital contribution to fund a portion of the purchase of Red Rock Gathering. See Notes 1 and 12 for additional information.

Rollforwards of the number of common limited partner, subordinated limited partner and general partner units for the six months ended June 30 follow.



	Common	Subordinated	General partner	Total
Units, January 1, 2013	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, June 30, 2013	29,073,974	24,409,850	1,091,453	54,575,277



	Common	Subordinated	General partner	Total
Units, January 1, 2014	29,079,866	24,409,850	1,091,453	54,581,169
Units issued in connection with the March Equity 2014 Offering (1)	5,300,000	—	108,337	5,408,337
Units issued under LTIP (1)(2)	43,503	—	861	44,364
Units, June 30, 2014	34,423,369	24,409,850	1,200,651	60,033,870

__________

(1) Including issuance to general partner in connection with contributions made to maintain 2% general partner interest.

(2) Units issued to common unitholders is net of 14,047 units withheld to meet minimum statutory tax withholding requirements.

Summit Investments' Equity in Contributed Subsidiaries. Summit Investments' equity in contributed subsidiaries represents its position in the net assets of Red Rock Gathering and Bison Midstream that have been acquired by SMLP. The balance also reflects net income attributable to Summit Investments for Red Rock Gathering and Bison Midstream for the periods beginning on their respective acquisition dates by Summit Investments and ending on the dates they were acquired by the Partnership. During the three- and six-month periods ended June 30, 2014 and 2013, net income was attributed to Summit Investments for (i) Red Rock Gathering for the period from January 1, 2014 to March 18, 2014 and for the period from January 1, 2013 to June 30, 2013 and (ii) Bison Midstream for the period from February 16, 2013 to June 4, 2013. Although included in partners' capital, net income attributable to Summit Investments has been excluded from the calculation of EPU. For additional information, see Notes 1, 7 and 12.

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 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 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%

SMLP allocated its distribution in accordance with the third target distribution level for distributions attributable to the quarter ended June 30, 2014. Details of cash distributions declared to date follow.



Attributable to the quarter ended	Payment date	Per-unit distribution		Cash paid to common unitholders		Cash paid to subordinated unitholders		Cash paid to general partner interest		Cash paid for IDRs		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		528		163		26,366
March 31, 2014	May 15, 2014	0.5000		17,211		12,205		608		360		30,384

On July 24, 2014, the board of directors of our general partner declared a distribution of $0.52 per unit for the quarterly period ended June 30, 2014. The distribution will be paid on August 14, 2014 to unitholders of record at the close of business on August 7, 2014.

EARNINGS PER UNIT

6 Months Ended

Jun. 30, 2014

Earnings Per Share [Abstract]

EARNINGS PER UNIT

The following table presents details on EPU.



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(Dollars in thousands, except per-unit amounts)
Net income	$	4,036	$	8,767	$	10,409	$	22,630
Less: net income attributable to Summit Investments	—		699		2,828		2,082
Net income attributable to SMLP	4,036		8,068		7,581		20,548
Less: net income attributable to general partner, including IDRs	801		161		1,232		411
Net income attributable to limited partners	$	3,235	$	7,907	$	6,349	$	20,137

Numerator for basic and diluted EPU:
Allocation of net income among limited partner interests:
Net income attributable to common units	$	1,891	$	4,012	$	4,398	$	10,127
Net income attributable to subordinated units	1,344		3,895		1,951		10,010
Net income attributable to limited partners	$	3,235	$	7,907	$	6,349	$	20,137

Denominator for basic and diluted EPU:
Weighted-average common units outstanding – basic	34,422,273		25,172,087		32,179,431		24,790,158
Effect of non-vested phantom units and non-vested restricted units	196,233		109,017		180,591		80,875
Weighted-average common units outstanding – diluted	34,618,506		25,281,104		32,360,022		24,871,033

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

Earnings per limited partner unit:
Common unit – basic	$	0.05	$	0.16	$	0.14	$	0.41
Common unit – diluted	$	0.05	$	0.16	$	0.14	$	0.41
Subordinated unit – basic and diluted	$	0.05	$	0.16	$	0.08	$	0.41

There were no units excluded from diluted earnings per unit as we do not have any anti-dilutive units for the three and six months ended June 30, 2014 or 2013. See Notes 6 and 8 for additional information.

UNIT-BASED COMPENSATION

6 Months Ended

Jun. 30, 2014

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

UNIT-BASED COMPENSATION

Long-Term Incentive Plan. SMLP’s 2012 Long-Term Incentive Plan (the "LTIP") provides for the granting of unit-based awards, including common units, restricted units and phantom units 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 the compensation committee of our general partner. A total of 5.0 million common units was reserved for issuance pursuant to and in accordance with the LTIP. As of June 30, 2014, approximately 4.6 million common units remained available for future issuance.

A rollfoward of phantom and restricted unit activity follows.



	Six months ended June 30, 2014
	Units		Weighted-average grant date fair value
Nonvested phantom and restricted units, beginning of period	283,682		$	23.41
Phantom units granted	136,867		$	42.32
Restricted units granted	—		$	—
Phantom and restricted units vested	(61,036	)	$	25.20
Phantom units forfeited	(10,760	)	$	25.85
Nonvested phantom and restricted units, end of period	348,753		$	30.44

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. A restricted unit is a common limited partner unit that is subject to a restricted period during which the unit remains subject to forfeiture.

The phantom units granted in connection with the IPO vest on the third anniversary of the IPO. All other phantom units granted to date vest ratably over a three-year period. Grant date fair value is determined based on the closing price of our common units on the date of grant multiplied by the number of phantom units awarded to the grantee. Holders of all phantom units granted to date are entitled to receive distribution equivalent rights for each phantom unit, providing for a lump sum cash amount equal to the accrued distributions from the grant date of the phantom units to be paid in cash upon the vesting date. Upon vesting, phantom unit awards may be settled, at our discretion, in cash and/or common units, but the current intention is to settle all phantom unit awards with common units.

As of June 30, 2014, the unrecognized unit-based compensation related to the LTIP was $6.9 million. Incremental unit-based compensation will be recorded over the remaining vesting period of approximately 2.7 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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
SMLP LTIP unit-based compensation	$	1,361	$	814	$	2,424	$	1,141

DFW Net Profits Interests. Class B membership interests in DFW Midstream (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. The DFW Net Profits Interests were accounted for as compensatory awards. All grants vested ratably and provided for accelerated vesting in certain limited circumstances, including a qualifying termination following a change in control (as defined in the underlying agreements). In April 2013, we repurchased all of the then-outstanding DFW Net Profits Interests from the five remaining holders. Upon the conclusion of these repurchase transactions, there were no remaining or outstanding DFW Net Profits Interests as of April 30, 2013.

CONCENTRATIONS OF RISK

6 Months Ended

Jun. 30, 2014

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 frequently 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 primarily comprise natural gas gathering, treating and processing services we provide to our customers. 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 can 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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
Revenue:
Counterparty A	13	%	13	%	13	%	15	%
Counterparty B	10	%	14	%	10	%	17	%

__________

* Less than 10%

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



	June 30,		December 31,
	2014		2013
Accounts receivable:
Counterparty A	16	%	37	%
Counterparty B	10	%	11	%

__________

* Less than 10%

RELATED-PARTY TRANSACTIONS

6 Months Ended

Jun. 30, 2014

RELATED-PARTY TRANSACTIONS

Recent Acquisitions. See Notes 1, 5, 6 and 12 for disclosure of the Red Rock Drop Down and Bison Drop Down and the funding of those transactions.

Reimbursement of Expenses from General Partner. 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 payables to our general partner for expenses that were paid on our behalf were as follows:



	June 30,		December 31,
	2014		2013
	(In thousands)
Due to affiliate	$	1,578	$	653

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



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Operation and maintenance expense	$	4,503	$	3,268	$	8,395	$	6,171
General and administrative expense	4,898		4,474		9,804		8,890

General and administrative expense includes $0.6 million of expenses allocated by the general partner for the three months ended June 30, 2013 and $1.8 million for the six months ended June 30, 2013.

Expense Allocations. During the period from January 1, 2014 to March 18, 2014 and the three and six months ended June 30, 2013, Summit Investments incurred interest expense which was related to capital projects at Red Rock Gathering. As such, the associated interest expense was allocated to Red Rock Gathering as a noncash contribution and capitalized into the basis of the asset.

Certain of Summit Investments’ current and former employees received Class B membership interests, classified as net profits interests, in Summit Investments (the “Net Profits Interests”). The Net Profits Interests participate in distributions upon time vesting and the achievement of certain distribution targets to Class A members or higher priority vested Net Profits Interests. The Net Profits Interests were accounted for as compensatory awards.

Summit Investments allocated a portion of the annual expense associated with the Net Profits Interests to Red Rock Gathering during the three and six months ended June 30, 2013. This amount is reflected in general and administrative expenses in the statement of operations.

Expenses Paid by Summit Investments on Behalf of Red Rock Gathering. Prior to the Red Rock Drop Down, Summit Investments incurred certain support expenses and capital expenditures on behalf of Red Rock Gathering during the six months ended June 30, 2014 and the three and six months ended June 30, 2013. These transactions were settled periodically through membership interests prior to the Red Rock Drop Down.

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Payments for electricity management consulting services	$	72	$	54	$	126	$	109

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 six months ended June 30, 2014.

- 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

COMMITMENTS AND CONTINGENCIES

6 Months Ended

Jun. 30, 2014

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Total rent expense	$	460	$	347	$	814	$	607

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

6 Months Ended

Jun. 30, 2014

Business Combinations [Abstract]

Acquisitions

ACQUISITIONS

Red Rock Gathering System. On March 18, 2014, the Partnership acquired Red Rock Gathering from an affiliate of Summit Investments for total cash consideration of $305.0 million, subject to customary working capital adjustments. The acquisition of Red Rock Gathering was funded with the net proceeds from the March 2014 Equity Offering, borrowings under our revolving credit facility and cash on hand. Because of the common control aspects in the drop down transaction, the Red Rock Gathering acquisition was deemed a transaction between entities under common control and, as such, was accounted for on an “as-if pooled” basis for all periods in which common control existed. SMLP’s financial results retrospectively include Red Rock Gathering’s financial results for all periods ending after October 23, 2012, the date Summit Investments acquired its interests, and before March 18, 2014. For additional information, see Notes 1, 5 and 6.

Bison Gas Gathering System. On February 15, 2013, Summit Investments acquired BTE. On June 4, 2013, a subsidiary of Summit Investments 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 Meadowlark Midstream and primarily gathers associated natural gas production from customers operating in 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 Note 1.

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 rights-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 Summit Investments and $1.0 million of general partner interests to SMLP’s general partner. Summit Investments had a net investment in the Bison Gas Gathering system of $303.2 million.

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 and Harrison counties 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 an affiliate of Summit Investments. For the three and six months ended June 30, 2013, SMLP recorded $0.4 million of revenue and $0.3 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.

Supplemental Disclosures – As-If Pooled Basis. As noted above, SMLP's acquisition of Red Rock Gathering and the Bison Gas Gathering system were transactions between commonly controlled entities which required that SMLP account for the acquisitions in a manner similar to a pooling of interests. As a result, the historical financial statements of the Partnership, Red Rock Gathering 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. Revenues and net income for the previously separate entities and the combined amounts for the three months ended June 30, 2013 and the six months ended June 30, 2014 and 2013, as presented in these unaudited condensed consolidated financial statements follow.



	Three months ended June 30, 2013			Six months ended June 30,
	Three months ended June 30, 2013			2014		2013
	(In thousands)
SMLP revenues	$	43,743		$	145,685	$	87,338
Red Rock Gathering revenues	12,176			11,313		23,035
Bison Gas Gathering system revenues (1)	15,542			—		23,073
Combined revenues	$	71,461		$	156,998	$	133,446

SMLP net income	$	8,068		$	7,581	$	20,548
Red Rock Gathering net income	1,234			2,828		2,030
Bison Gas Gathering system net income (1)	(535		)	—		52
Combined net income	$	8,767		$	10,409	$	22,630

__________

(1) Results are fully reflected in SMLP's results of operations for the three and six months ended June 30, 2014.

Unaudited Pro Forma Financial Information. The following unaudited pro forma financial information assumes that:


•	The acquisition of the Bison Gas Gathering system occurred on January 1, 2012. The pro forma results for Bison Midstream were derived from revenues and net income in 2013.


•	The acquisition of Mountaineer Midstream occurred on January 1, 2012. The pro forma results for Mountaineer Midstream were derived from revenues and net income in 2013.


•	The acquisition of Red Rock Gathering occurred on January 1, 2011. The pro forma results reflect actual Red Rock Gathering revenues and net income earned and recognized in 2014 and 2013.


•	Pro forma net income for the three and six months ended June 30, 2013 has been adjusted to remove the impact of $2.4 million of nonrecurring transaction costs associated with the acquisitions of Bison Midstream and Mountaineer Midstream.

•

Pro forma adjustments in 2013 also reflect the impact of $310.0 million of incremental borrowings on our revolving credit facility for the Bison Midstream and Mountaineer Midstream acquisitions 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 for Bison Midstream.


•	Pro forma adjustments in 2014 and 2013 also reflect the impact of a 5,300,000 common unit issuance, the general partner capital contribution to maintain its 2% general partner interest and $100.0 million of incremental borrowings on our revolving credit facility to fund the acquisition of Red Rock Gathering.



	Three months ended June 30, 2013		Six months ended June 30,
	Three months ended June 30, 2013		2014		2013
	(In thousands, except for per-unit amounts)
Total Red Rock Gathering revenues included in consolidated revenues	$	12,176	$	34,589	$	23,034
Total Bison Midstream and Mountaineer Midstream revenues included in consolidated revenues	15,951				23,482

Total Red Rock Gathering net income included in consolidated net income	$	1,234	$	10,181	$	2,031
Total Bison Midstream and Mountaineer Midstream net income included in consolidated net income	54				641

Pro forma total revenues	$	74,480	$	156,998	$	145,596
Pro forma net income	9,805		9,905		18,110

Pro forma common EPU - basic and diluted	$	0.16	$	0.16	$	0.30
Pro forma subordinated EPU - basic and diluted	0.16		0.12		0.30

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 acquisition of Red Rock Gathering had occurred on January 1, 2011, 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
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+ Details

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

6 Months Ended

Jun. 30, 2014

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Fair Value of Financial Instruments

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



	June 30, 2014				December 31, 2013
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	426,000	$	426,000	$	286,000	$	286,000
7.5% Senior notes	300,000		326,500		300,000		314,625

Commitments and Contingencies

Revenue Recognition

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

•



	Six months ended June 30, 2014
	Current		Noncurrent
	(In thousands)
Deferred revenue, beginning of period	$	1,555	$	29,683
Additions	2,609		7,410
Less: revenue recognized due to expiration	1,555		—
Deferred revenue, end of period	$	2,609	$	37,093

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 (Tables)

6 Months Ended

Jun. 30, 2014

Accounting Policies [Abstract]

Summary of Estimated Fair Value for Financial instruments

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



	June 30, 2014				December 31, 2013
	Carrying value		Estimated fair value (Level 2)		Carrying value		Estimated fair value (Level 2)
	(In thousands)
Revolving credit facility	$	426,000	$	426,000	$	286,000	$	286,000
7.5% Senior notes	300,000		326,500		300,000		314,625

Deferred Revenue, by Arrangement, Disclosure

A rollforward of current and noncurrent deferred revenue follows.



	Six months ended June 30, 2014
	Current		Noncurrent
	(In thousands)
Deferred revenue, beginning of period	$	1,555	$	29,683
Additions	2,609		7,410
Less: revenue recognized due to expiration	1,555		—
Deferred revenue, end of period	$	2,609	$	37,093

PROPERTY, PLANT, AND EQUIPMENT, NET (Tables)

6 Months Ended

Jun. 30, 2014

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)	June 30,		December 31,
	Useful lives (In years)	2014		2013
	(Dollars in thousands)
Natural gas gathering and processing systems	30	$	810,617	$	744,359
Compressor stations and compression equipment	30	393,483		380,000
Construction in progress	n/a	63,419		83,765
Other	4-15	24,175		21,304
Total		1,291,694		1,229,428
Less: accumulated depreciation		92,967		71,347
Property, plant, and equipment, net		$	1,198,727	$	1,158,081

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Depreciation expense	$	11,104	$	8,508	$	21,625	$	16,325
Capitalized interest	2,329		1,066		3,688		1,559

IDENTIFIABLE INTANGIBLE ASSETS, NONCURRENT LIABILITY AND GOODWILL (Tables)

6 Months Ended

Jun. 30, 2014

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:



	June 30, 2014
	Useful lives (In years)	Gross carrying amount		Accumulated amortization			Net
	(Dollars in thousands)
Favorable gas gathering contracts	18.7	$	24,195	$	(7,185	)	$	17,010
Contract intangibles	12.5	426,464		(59,318		)	367,146
Rights-of-way	24.2	111,975		(10,052		)	101,923
Total amortizable intangible assets		$	562,634	$	(76,555	)	$	486,079

Unfavorable gas gathering contract	10.0	$	10,962	$	(5,007	)	$	5,955



	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	24.3	108,706		(7,715		)	100,991
Total amortizable intangible assets		$	559,365	$	(57,188	)	$	502,177

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

Schedule of recognized amortization expense within the statements of operations

We recognized amortization expense in revenues as follows:



	Three months ended June 30,						Six months ended June 30,
	2014			2013			2014			2013
	(In thousands)
Amortization expense – favorable gas gathering contracts	$	(436	)	$	(527	)	$	(870	)	$	(1,099	)
Amortization expense – unfavorable gas gathering contract	211			277			419			569
Amortization of favorable and unfavorable contracts	$	(225	)	$	(250	)	$	(451	)	$	(530	)

We recognized amortization expense in costs and expenses as follows:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Amortization expense – contract intangibles	$	8,198	$	7,421	$	16,160	$	12,709
Amortization expense – rights-of-way	1,178		872		2,337		1,680

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 for the remainder of 2014 and each of the four succeeding fiscal years follows.



	Assets		Liability
	(In thousands)
2014	$	20,589	$	806
2015	43,872		1,650
2016	44,114		1,571
2017	42,846		1,438
2018	43,115		490

LONG-TERM DEBT (Tables)

6 Months Ended

Jun. 30, 2014

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

Long-term debt consisted of the following:



	June 30,		December 31,
	2014		2013
	(In thousands)
Variable rate senior secured revolving credit facility (2.40% at June 30, 2014 and 2.42% at December 31, 2013) due November 2018	$	426,000	$	286,000
7.50% Senior unsecured notes due July 2021	300,000		300,000
Total long-term debt	$	726,000	$	586,000

- 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 (Tables)

6 Months Ended

Jun. 30, 2014

Equity [Abstract]

Schedule of Partner Units Activity

Rollforwards of the number of common limited partner, subordinated limited partner and general partner units for the six months ended June 30 follow.



	Common	Subordinated	General partner	Total
Units, January 1, 2013	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, June 30, 2013	29,073,974	24,409,850	1,091,453	54,575,277



	Common	Subordinated	General partner	Total
Units, January 1, 2014	29,079,866	24,409,850	1,091,453	54,581,169
Units issued in connection with the March Equity 2014 Offering (1)	5,300,000	—	108,337	5,408,337
Units issued under LTIP (1)(2)	43,503	—	861	44,364
Units, June 30, 2014	34,423,369	24,409,850	1,200,651	60,033,870

__________

(1) Including issuance to general partner in connection with contributions made to maintain 2% general partner interest.

(2) Units issued to common unitholders is net of 14,047 units withheld to meet minimum statutory tax withholding requirements.

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 to date follow.



Attributable to the quarter ended	Payment date	Per-unit distribution		Cash paid to common unitholders		Cash paid to subordinated unitholders		Cash paid to general partner interest		Cash paid for IDRs		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		528		163		26,366
March 31, 2014	May 15, 2014	0.5000		17,211		12,205		608		360		30,384

EARNINGS PER UNIT (Tables)

6 Months Ended

Jun. 30, 2014

Earnings Per Share [Abstract]

Schedule of earnings per Unit

The following table presents details on EPU.



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(Dollars in thousands, except per-unit amounts)
Net income	$	4,036	$	8,767	$	10,409	$	22,630
Less: net income attributable to Summit Investments	—		699		2,828		2,082
Net income attributable to SMLP	4,036		8,068		7,581		20,548
Less: net income attributable to general partner, including IDRs	801		161		1,232		411
Net income attributable to limited partners	$	3,235	$	7,907	$	6,349	$	20,137

Numerator for basic and diluted EPU:
Allocation of net income among limited partner interests:
Net income attributable to common units	$	1,891	$	4,012	$	4,398	$	10,127
Net income attributable to subordinated units	1,344		3,895		1,951		10,010
Net income attributable to limited partners	$	3,235	$	7,907	$	6,349	$	20,137

Denominator for basic and diluted EPU:
Weighted-average common units outstanding – basic	34,422,273		25,172,087		32,179,431		24,790,158
Effect of non-vested phantom units and non-vested restricted units	196,233		109,017		180,591		80,875
Weighted-average common units outstanding – diluted	34,618,506		25,281,104		32,360,022		24,871,033

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

Earnings per limited partner unit:
Common unit – basic	$	0.05	$	0.16	$	0.14	$	0.41
Common unit – diluted	$	0.05	$	0.16	$	0.14	$	0.41
Subordinated unit – basic and diluted	$	0.05	$	0.16	$	0.08	$	0.41

UNIT-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2014

Phantom and restricted units

MEMBERSHIP INTERESTS

Schedule of activity

A rollfoward of phantom and restricted unit activity follows.



	Six months ended June 30, 2014
	Units		Weighted-average grant date fair value
Nonvested phantom and restricted units, beginning of period	283,682		$	23.41
Phantom units granted	136,867		$	42.32
Restricted units granted	—		$	—
Phantom and restricted units vested	(61,036	)	$	25.20
Phantom units forfeited	(10,760	)	$	25.85
Nonvested phantom and restricted units, end of period	348,753		$	30.44

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
SMLP LTIP unit-based compensation	$	1,361	$	814	$	2,424	$	1,141

CONCENTRATIONS OF RISK (Tables)

6 Months Ended

Jun. 30, 2014

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
Revenue:
Counterparty A	13	%	13	%	13	%	15	%
Counterparty B	10	%	14	%	10	%	17	%

__________

* 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:



	June 30,		December 31,
	2014		2013
Accounts receivable:
Counterparty A	16	%	37	%
Counterparty B	10	%	11	%

__________

* Less than 10%

RELATED-PARTY TRANSACTIONS (Tables)

6 Months Ended

Jun. 30, 2014

Schedules of Related Party Transactions

Amounts paid for such services were as follows:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Payments for electricity management consulting services	$	72	$	54	$	126	$	109

The payables to our general partner for expenses that were paid on our behalf were as follows:



	June 30,		December 31,
	2014		2013
	(In thousands)
Due to affiliate	$	1,578	$	653

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



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Operation and maintenance expense	$	4,503	$	3,268	$	8,395	$	6,171
General and administrative expense	4,898		4,474		9,804		8,890

COMMITMENTS AND CONTINGENCIES (Tables)

6 Months Ended

Jun. 30, 2014

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:



	Three months ended June 30,				Six months ended June 30,
	2014		2013		2014		2013
	(In thousands)
Total rent expense	$	460	$	347	$	814	$	607

ACQUISITIONS (Tables)

6 Months Ended

Jun. 30, 2014

Business Acquisition [Line Items]

Business Acquisition, Pro Forma Information



	Three months ended June 30, 2013		Six months ended June 30,
	Three months ended June 30, 2013		2014		2013
	(In thousands, except for per-unit amounts)
Total Red Rock Gathering revenues included in consolidated revenues	$	12,176	$	34,589	$	23,034
Total Bison Midstream and Mountaineer Midstream revenues included in consolidated revenues	15,951				23,482

Total Red Rock Gathering net income included in consolidated net income	$	1,234	$	10,181	$	2,031
Total Bison Midstream and Mountaineer Midstream net income included in consolidated net income	54				641

Pro forma total revenues	$	74,480	$	156,998	$	145,596
Pro forma net income	9,805		9,905		18,110

Pro forma common EPU - basic and diluted	$	0.16	$	0.16	$	0.30
Pro forma subordinated EPU - basic and diluted	0.16		0.12		0.30

Bison Midstream

Business Acquisition [Line Items]

Fair Value of Assets Acquired and Liabilities Assumed

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 three months ended June 30, 2013 and the six months ended June 30, 2014 and 2013, as presented in these unaudited condensed consolidated financial statements follow.



	Three months ended June 30, 2013			Six months ended June 30,
	Three months ended June 30, 2013			2014		2013
	(In thousands)
SMLP revenues	$	43,743		$	145,685	$	87,338
Red Rock Gathering revenues	12,176			11,313		23,035
Bison Gas Gathering system revenues (1)	15,542			—		23,073
Combined revenues	$	71,461		$	156,998	$	133,446

SMLP net income	$	8,068		$	7,581	$	20,548
Red Rock Gathering net income	1,234			2,828		2,030
Bison Gas Gathering system net income (1)	(535		)	—		52
Combined net income	$	8,767		$	10,409	$	22,630

__________

(1) Results are fully reflected in SMLP's results of operations for the three and six months ended June 30, 2014.

Mountaineer Midstream

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 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

ORGANIZATION, BUSINESS OPERATIONS AND BASIS OF PRESENTATION (Details)		1 Months Ended		6 Months Ended
	Oct. 03, 2012	Jun. 30, 2014 shares	Mar. 31, 2014	Jun. 30, 2014 segment shares	Dec. 31, 2013 shares
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding		34,423,369		34,423,369	29,079,866
General partner interests, units outstanding		1,200,651		1,200,651	1,091,453
Number of operating segments \| segment				4
Number of reportable segments \| segment				1
Summit 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 Investments
ORGANIZATION AND BUSINESS OPERATIONS
General partner interests, units outstanding		1,200,651		1,200,651
Common units \| Summit Investments
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding		9,641,397		9,641,397
Subordinated units \| Summit Investments
ORGANIZATION AND BUSINESS OPERATIONS
Common limited partner capital, units outstanding		24,409,850		24,409,850
General partner
ORGANIZATION AND BUSINESS OPERATIONS
General partner interest (as a percent)			2.00%	2.00%
Class A Membership Interest [Member] \| GE Energy Financial Services [Member]
ORGANIZATION AND BUSINESS OPERATIONS
Exchange of membership interests, percent		100.00%

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility, Carrying value	$ 426,000	$ 286,000
Senior notes, Carrying value	300,000	300,000
Fair value, Level 2 inputs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility, Estimated fair value (Level 2)	426,000	286,000
Senior notes, Estimated fair value (Level 2)	$ 326,500	$ 314,625

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2014
Significant Accounting Policies [Line Items]
Shortfall payments billed and included in accounts receivable		$ 4.8
Period to utilize the current portion of shortfall payments to offset gathering fees to the extent that customer's throughput volumes exceed its MVC		7 years
Deferred tax liability, noncurrent		$ 1.2
General partner
Significant Accounting Policies [Line Items]
General partner interest (as a percent)	2.00%	2.00%

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) $ in Thousands	6 Months Ended
	Jun. 30, 2014 USD ($)
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, Beginning balance, Current	$ 1,555
Additions, Current	2,609
Less: revenue recognized due to expiration, Current	1,555
Deferred revenue, Ending balance, Current	2,609
Deferred revenue, Beginning balance, Noncurrent	29,683
Additions, Noncurrent	7,410
Less: revenue recognized due to expiration, Noncurrent	0
Deferred revenue, Ending balance, Noncurrent	$ 37,093

PROPERTY, PLANT, AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	$ 1,291,694		$ 1,291,694		$ 1,229,428
Less accumulated depreciation	92,967		92,967		71,347
Property, plant, and equipment, net	1,198,727		1,198,727		1,158,081
Depreciation expense	11,104	$ 8,508	21,625	$ 16,325
Capitalized interest	2,329	$ 1,066	$ 3,688	$ 1,559
Gas gathering system
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives			30 years
Gross	810,617		$ 810,617		744,359
Compressor stations and compression equipment
PROPERTY, PLANT, AND EQUIPMENT, NET
Useful lives			30 years
Gross	393,483		$ 393,483		380,000
Construction in progress
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	63,419		63,419		83,765
Other
PROPERTY, PLANT, AND EQUIPMENT, NET
Gross	$ 24,175		$ 24,175		$ 21,304
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	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 562,634		$ 562,634		$ 559,365
Accumulated amortization	(76,555)		(76,555)		(57,188)
Total intangible assets, net	486,079		$ 486,079		$ 502,177
Noncurrent liability
Unfavorable gas gathering contract, useful lives			10 years		10 years
Unfavorable contract, Gross Carrying Amount	10,962		$ 10,962		$ 10,962
Unfavorable gas gathering contract, Accumulated Amortization	(5,007)		(5,007)		(4,588)
Unfavorable gas gathering contract, Net	5,955		5,955		$ 6,374
Amortization expense
Amortization expense - unfavorable contract	211	$ 277	419	$ 569
Amortization of favorable and unfavorable contracts	(225)	(250)	(451)	(530)
Assets
2014	20,589		20,589
2015	43,872		43,872
2016	44,114		44,114
2017	42,846		42,846
2018	43,115		43,115
Liability
2014	806		806
2015	1,650		1,650
2016	1,571		1,571
2017	1,438		1,438
2018	490		$ 490
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		$ 24,195
Accumulated amortization	(7,185)		(7,185)		(6,315)
Total intangible assets, net	17,010		17,010		$ 17,880
Amortization expense
Amortization expense	436	527	$ 870	1,099
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Useful lives			12 years 6 months		12 years 6 months
Gross carrying amount	426,464		$ 426,464		$ 426,464
Accumulated amortization	(59,318)		(59,318)		(43,158)
Total intangible assets, net	367,146		367,146		$ 383,306
Amortization expense
Amortization expense	8,198	7,421	$ 16,160	12,709
Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Useful lives			24 years 2 months		24 years 4 months
Gross carrying amount	111,975		$ 111,975		$ 108,706
Accumulated amortization	(10,052)		(10,052)		(7,715)
Total intangible assets, net	101,923		101,923		$ 100,991
Amortization expense
Amortization expense	$ 1,178	$ 872	$ 2,337	$ 1,680

LONG-TERM DEBT (Details) - USD ($) $ in Thousands	6 Months Ended
LONG-TERM DEBT (Details) - USD ($) $ in Thousands	Jun. 30, 2014	Dec. 31, 2013
REVOLVING CREDIT FACILITY
Revolving credit facility	$ 426,000	$ 286,000
Senior unsecured notes	300,000	300,000
Total long-term debt	$ 726,000	$ 586,000
Revolving credit facility \| Summit Holdings
REVOLVING CREDIT FACILITY
Variable rate basis	LIBOR
Weighted-average interest rate (as a percent)	2.40%	2.42%
Unused portion under the facility	$ 274,000
Commitment fee on unused portion of the facility (as a percent)	0.375%
Revolving credit facility \| LIBOR \| Summit Holdings
REVOLVING CREDIT FACILITY
Applicable margin (as a percent)	2.25%

LONG-TERM DEBT (Senior Notes) (Details) - USD ($)		1 Months Ended
LONG-TERM DEBT (Senior Notes) (Details) - USD ($)	Jul. 15, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Senior unsecured notes			$ 300,000,000	$ 300,000,000
Finance Corp.
Debt Instrument [Line Items]
Cumulative percentage ownership in subsidiary		100.00%
7.5% Senior Notes [Member] \| Summit Holdings and Finance Corporation [Member] \| Senior Notes
Debt Instrument [Line Items]
Senior unsecured notes		$ 300,000,000.0
Senior note, stated interest rate		7.50%
Subsequent Event \| 5.5% Senior Notes [Member] \| Summit Holdings and Finance Corporation [Member] \| Senior Notes
Debt Instrument [Line Items]
Senior unsecured notes	$ 300,000,000.0
Senior note, stated interest rate	5.50%
Maximum percent of aggregate principal amount redeemable	35.00%
Events of default, period of payment default	30 days
Events of default, failure to comply with covenants, period after notice	180 days
Events of default, failure to comply with other agreements in the indenture, period after notice	30 days
Events of default, failure to pay final judgments, in excess of 20.0 million	$ 20,000,000.0
Declaration of immediate payment, holding percent of principal amount required	25.00%
Prior to August 15, 2017 [Member] \| Subsequent Event \| 5.5% Senior Notes [Member] \| Summit Holdings and Finance Corporation [Member] \| Senior Notes
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	105.50%
August 15, 2017 - August 15, 2020 [Member] \| Subsequent Event \| 5.5% Senior Notes [Member] \| Summit Holdings and Finance Corporation [Member] \| Senior Notes
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	104.125%
After August 15, 2020 [Member] \| Subsequent Event \| 5.5% Senior Notes [Member] \| Summit Holdings and Finance Corporation [Member] \| Senior Notes
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	100.00%

PARTNERS' CAPITAL (Partners' Capital and Schedule of Units) (Details) - $ / shares

1 Months Ended

6 Months Ended

Mar. 31, 2014

Jun. 30, 2014

Jun. 30, 2013

Rollforwards of the number of partner units

Common limited partner capital units outstanding, beginning balance

29,079,866

Subordinated limited partner capital units outstanding, begining balance

24,409,850

General partner interests units outstanding, beginning balance

1,091,453

Partner capital units outstanding, beginning balance

54,581,169.000

49,818,597.000

Units issued in connection with the March 2014 Offering

^[1]

5,408,337.000

Units issued under LTIP

^[1],[2]

44,364.000

Common limited partner capital units outstanding, ending balance

34,423,369

Subordinated limited partner capital units outstanding, ending balance

24,409,850

General partner interests units outstanding, ending balance

1,200,651

Partner capital units outstanding, ending balance

60,033,870

54,575,277

Units withheld to meet the minimum statutory tax withholding requirement

14,047

Common

Class of Stock [Line Items]

Common units sold in public offering

10,350,000

Price per unit (dollars per unit)

$ 38.75

Rollforwards of the number of partner units

Common limited partner capital units outstanding, beginning balance

29,079,866

24,412,427

Units issued in connection with the March 2014 Offering

^[1]

5,300,000

Units issued under LTIP

^[1],[2]

43,503

Common limited partner capital units outstanding, ending balance

34,423,369

29,073,974

Subordinated

Rollforwards of the number of partner units

Subordinated limited partner capital units outstanding, begining balance

24,409,850

Units issued in connection with the March 2014 Offering

^[1]

Units issued under LTIP

^[1],[2]

Subordinated limited partner capital units outstanding, ending balance

24,409,850

General partner

Rollforwards of the number of partner units

General partner interests units outstanding, beginning balance

1,091,453

996,320

Units issued in connection with the March 2014 Offering

^[1]

108,337

Units issued under LTIP

^[1],[2]

861

General partner interests units outstanding, ending balance

1,200,651

1,091,453

Partnership | Common

Class of Stock [Line Items]

Common units sold in public offering

5,300,000

Summit Investments

Rollforwards of the number of partner units

General partner interests units outstanding, ending balance

1,200,651

Summit Investments | Common

Class of Stock [Line Items]

Common units sold in public offering

5,050,000

General partner

Class of Stock [Line Items]

General partner interest (as a percent)

2.00%

Bison Midstream

Rollforwards of the number of partner units

Units issued in connection with acquisition

1,585,560.00

Bison Midstream | Common

Rollforwards of the number of partner units

Units issued in connection with acquisition

1,553,849

Bison Midstream | Subordinated

Rollforwards of the number of partner units

Units issued in connection with acquisition

Bison Midstream | General partner

Rollforwards of the number of partner units

Units issued in connection with acquisition

31,711

Mountaineer Midstream

Rollforwards of the number of partner units

Units issued in connection with acquisition

3,171,120.00

Mountaineer Midstream | Common

Rollforwards of the number of partner units

Units issued in connection with acquisition

3,107,698

Mountaineer Midstream | Subordinated

Rollforwards of the number of partner units

Units issued in connection with acquisition

Mountaineer Midstream | General partner

Rollforwards of the number of partner units

Units issued in connection with acquisition

63,422

[1]	Including issuance to general partner in connection with contributions made to maintain 2% general partner interest.
[2]	Units issued to common unitholders is net of 14,047 units withheld to meet minimum statutory tax withholding requirements.

PARTNERS' CAPITAL (Subordination and Cash Distribution Policy) (Details) - $ / shares	1 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2014
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%
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 (Minimum Quarterly Distribution) (Details)	6 Months Ended
	Jun. 30, 2014 $ / shares
Equity [Abstract]
Minimum quarterly distributions (in dollars per share)	$ 0.40
Minimum annual distributions (in dollars per share)	$ 1.60

PARTNERS' CAPITAL (Partnership Target Distributions) (Details)	6 Months Ended
	Jun. 30, 2014 $ / shares
Minimum quarterly distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	$ 0.4
Thereafter
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.60
Minimum \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.40
Minimum \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.46
Minimum \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.50
Maximum \| First target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.46
Maximum \| Second target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	0.5
Maximum \| Third target distribution
Schedule of Partnership Target Distributions [Line Items]
Total quarterly distribution per unit target amount (in dollars per unit)	$ 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%

PARTNERS' CAPITAL (Cash Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands								3 Months Ended		6 Months Ended
	Jul. 24, 2014	May 15, 2014	Feb. 14, 2014	Nov. 14, 2013	Aug. 14, 2013	May 15, 2013	Feb. 14, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Distribution Made to Limited Partner [Line Items]
Per-unit distribution (in dollars per unit)		$ 0.5	$ 0.48	$ 0.46	$ 0.435	$ 0.42	$ 0.41	$ 0.5	$ 0.42	$ 0.98	$ 0.83
Distributions to unitholders		$ 30,384	$ 26,366	$ 25,108	$ 23,740	$ 20,923	$ 20,425			$ 56,749	$ 41,348
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Per-unit distribution (in dollars per unit)	$ 0.52
General partner
Distribution Made to Limited Partner [Line Items]
General partner's IDRs		360	163	0	0	0	0
Limited partners, Common
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		17,211	13,958	13,377	12,647	10,253	10,009
Subordinated
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		12,205	11,717	11,229	10,618	10,252	10,008
General Partner Units
Distribution Made to Limited Partner [Line Items]
Distributions to unitholders		$ 608	$ 528	$ 502	$ 475	$ 418	$ 408

EARNINGS PER UNIT (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 4,036	$ 8,767	$ 10,409	$ 22,630
Less: net income attributable to SMP Holdings	0	699	2,828	2,082
Net income attributable to SMLP	4,036	8,068	7,581	20,548
Less: net income attributable to general partner, including IDRs	801	161	1,232	411
Net income attributable to limited partners	3,235	7,907	6,349	20,137
Common units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to limited partners	$ 1,891	$ 4,012	$ 4,398	$ 10,127
Weighted-average units outstanding - basic	34,422,273	25,172,087	32,179,431	24,790,158
Less: effect of non-vested phantom units and non-vested restricted units (in units)	196,233	109,017	180,591	80,875
Weighted-average units outstanding - diluted	34,618,506	25,281,104	32,360,022	24,871,033
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.14	$ 0.41
Subordinated Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to limited partners	$ 1,344	$ 3,895	$ 1,951	$ 10,010
Weighted-average units outstanding - basic	24,409,850	24,409,850	24,409,850	24,409,850
Weighted-average units outstanding - diluted	24,409,850	24,409,850	24,409,850	24,409,850
Earnings per limited partner unit
Basic (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41
Diluted (in dollars per share)	$ 0.05	$ 0.16	$ 0.08	$ 0.41

UNIT-BASED COMPENSATION (Narrative) (Details) $ in Millions	6 Months Ended
UNIT-BASED COMPENSATION (Narrative) (Details) $ in Millions	Jun. 30, 2014 USD ($) shares
Long-term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized non-cash compensation expense \| $	$ 6.9
Remaining expected weighted-average vesting period of recognition of incremental non-cash compensation expense	2 years 8 months 15 days
Units forfeited (in shares)	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	4,600,000
Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Units forfeited (in shares)	10,760

UNIT-BASED COMPENSATION (Phantom and Restricted Unit Activity) (Details)	6 Months Ended
	Jun. 30, 2014 $ / shares shares
Phantom and restricted units
Phantom and Restricted Unit Activity
Unit vested (in shares) \| shares	(61,036)
Weighted-average grant date fair value
Units vested, Weighted-average grant date fair value (in dollars per share) \| $ / shares	$ 25.20
Phantom Units
Phantom and Restricted Unit Activity
Nonvested phantom and restricted units, beginning of period (in shares) \| shares	283,682
Units granted (in shares) \| shares	136,867
Units forfeited (in shares) \| shares	(10,760)
Nonvested phantom and restricted units, end of period (in shares) \| shares	348,753
Weighted-average grant date fair value
Nonvested, Weighted-average grant date fair value, beginning (in dollars per share) \| $ / shares	$ 23.41
Units granted, Weighted-average grant date fair value (in dollars per share) \| $ / shares	42.32
Units forfeited, Weighted-average grant date fair value (in dollars per share) \| $ / shares	25.85
Nonvested, Weighted-average grant date fair value, ending (in dollars per share) \| $ / shares	$ 30.44
Restricted Units [Member]
Phantom and Restricted Unit Activity
Units granted (in shares) \| shares	0
Weighted-average grant date fair value
Units granted, Weighted-average grant date fair value (in dollars per share) \| $ / shares	$ 0.00

UNIT-BASED COMPENSATION (Unit-based Compensation) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation			$ 2,424
Long-term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unit-based compensation	$ 1,361	$ 814	$ 2,424	$ 1,141

CONCENTRATIONS OF RISK (Details)	3 Months Ended		6 Months Ended		12 Months Ended
CONCENTRATIONS OF RISK (Details)	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Counterparty A \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Concentration risk, percentage	13.00%	13.00%	13.00%	15.00%
Counterparty A \| Accounts receivable \| Credit concentration
CONCENTRATIONS OF RISK
Concentration risk, percentage			16.00%		37.00%
Counterparty B \| Revenue \| Customer concentration
CONCENTRATIONS OF RISK
Concentration risk, percentage	10.00%	14.00%	10.00%	17.00%
Counterparty B \| Accounts receivable \| Credit concentration
CONCENTRATIONS OF RISK
Concentration risk, percentage			10.00%		11.00%

RELATED-PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
RELATED-PARTY TRANSACTIONS
Due to affiliate	$ 1,578		$ 1,578		$ 653
General partner
RELATED-PARTY TRANSACTIONS
Due to affiliate	1,578		1,578			$ 653
General partner \| Operation and maintenance expense allocation [Member]
RELATED-PARTY TRANSACTIONS
General and administrative expense allocation	4,503	$ 3,268	8,395	$ 6,171
General partner \| General and administrative expense allocation [Member]
RELATED-PARTY TRANSACTIONS
General and administrative expense allocation	4,898	4,474	9,804	8,890
Equipower
RELATED-PARTY TRANSACTIONS
Payments for electricity management consulting services	$ 72	54	126	109
IPS Engineering/EPC
RELATED-PARTY TRANSACTIONS
Payments for electricity management consulting services			$ 200
Expenses allocated by General Partner \| General partner \| General and administrative expense allocation [Member]
RELATED-PARTY TRANSACTIONS
General and administrative expense allocation		$ 600		$ 1,800

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Total rent expense related to operating leases	$ 460	$ 347	$ 814	$ 607

ACQUISITIONS (Red Rock Gathering) (Details) $ in Millions	Mar. 18, 2014 USD ($)
Red Rock Gathering Company, LLC
Business Acquisition [Line Items]
Cost of acquired entity, cash paid	$ 305.0

ACQUISITIONS (Bison Midstream) (Details) - USD ($) $ in Thousands		6 Months Ended
	Jun. 04, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Feb. 15, 2013
Business Acquisition [Line Items]
Purchase price assigned to Bison Gas Gathering system			$ 303,168
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill		$ 115,888		$ 115,888
SMP Holdings' equity in Bison Midstream
Business Acquisition [Line Items]
Purchase price assigned to Bison Gas Gathering system			$ 303,168
Bison Midstream
Business Acquisition [Line Items]
Cost of acquired entity, purchase price	$ 248,900
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					$ 54,199
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, cash paid	200,000
Purchase price assigned to Bison Gas Gathering system	$ 303,200
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 (Mountaineer Midstream) (Details) $ in Thousands		3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 21, 2013 USD ($) compressor_station	Jun. 30, 2013 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2013 USD ($)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill			$ 115,888		$ 115,888
Contract intangibles
Business Acquisition [Line Items]
Useful lives			12 years 6 months		12 years 6 months
Rights-of-way
Business Acquisition [Line Items]
Useful lives			24 years 2 months		24 years 4 months
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		$ 400		$ 400
Mountaineer Midstream net income since acquisition		$ 300		$ 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 (Revenue and Net Income) (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Business Acquisition [Line Items]

Revenues

$ 80,796

$ 71,461

$ 156,998

$ 133,446

Net income

$ 4,036

8,767

10,409

22,630

Summit Midstream Partners, LP

Business Acquisition [Line Items]

Revenues

43,743

145,685

87,338

Net income

8,068

7,581

20,548

Red Rock Gathering Company, LLC

Business Acquisition [Line Items]

Revenues

12,176

11,313

23,035

Net income

1,234

2,828

2,030

Bison Midstream, LLC

Business Acquisition [Line Items]

Revenues

^[1]

15,542

23,073

Net income

^[1]

$ (535)

$ 0

$ 52

[1]	Results are fully reflected in SMLP's results of operations for the three and six months ended June 30, 2014.

ACQUISITIONS (Pro Forma) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended		18 Months Ended
	Mar. 31, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues		$ 80,796	$ 71,461	$ 156,998	$ 133,446
Net income		$ 4,036	8,767	10,409	22,630
Pro forma total revenues			74,480	156,998	145,596
Pro forma net income			$ 9,805	$ 9,905	$ 18,110
Limited partners, Common
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma EPU, basic and diluted			$ 0.16	$ 0.16	$ 0.30
Subordinated units
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma EPU, basic and diluted			$ 0.16	$ 0.12	$ 0.30
Bison Midstream
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Incremental borrowings on revolving credit facility					$ 310,000
Red Rock Gathering Company, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Incremental borrowings on revolving credit facility						$ 100,000
Common unit issuance						5,300,000
Red Rock Gathering Company, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues			$ 12,176	$ 11,313	23,035
Net income			1,234	2,828	2,030
Red Rock Gathering Company, LLC \| Red Rock Gathering Company, LLC
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues			12,176	34,589	23,034
Net income			1,234	$ 10,181	2,031
Bison Midstream and Mountaineer Midstream \| Bison Midstream and Mountaineer Midstream
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues			15,951		23,482
Net income			54		641
Acquisition-related Costs \| Bison Midstream and Mountaineer Midstream
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Nonrecurring transaction cost			$ 2,400		2,400
General partner
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
General partner interest (as a percent)	2.00%			2.00%
Net income				$ 1,232	$ 411