Summit Midstream Partners (SMLP) 10-Q 10 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Entity Registrant Name	Summit Midstream Partners, LP
Entity Central Index Key	0001549922
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		55,880,540
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Title of 12(b) Security	Common Units
Trading Symbol	SMLP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-35666
Entity Tax Identification Number	45-5200503
Entity Address, Address Line One	910 Louisiana Street
Entity Address, Address Line Two	Suite 4200
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77002
City Area Code	832
Local Phone Number	413-4770
Document Quarterly Report	true
Entity Interactive Data Current	Yes
Document Transition Report	false
Entity Incorporation, State or Country Code	DE

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 36,571	$ 9,530
Restricted cash	5,048	27,392
Accounts receivable	77,199	97,418
Other current assets	4,252	5,521
Total current assets	123,070	139,861
Property, plant and equipment, net	1,855,889	1,882,489
Intangible assets, net	215,901	232,278
Investment in equity method investees	383,058	309,728
Other noncurrent assets	8,584	9,742
Total assets	2,586,502	2,574,098
Current liabilities:
Trade accounts payable	18,422	24,415
Accrued expenses	11,331	11,339
Deferred revenue	15,354	13,493
Ad valorem taxes payable	6,307	8,477
Accrued interest	11,737	12,346
Accrued environmental remediation	1,795	1,725
Other current liabilities	9,859	12,206
Short-term debt and current portion of long-term debt	38,000	5,546
Total current liabilities	112,805	89,547
Long-term debt	1,545,133	1,622,279
Noncurrent deferred revenue	42,348	38,709
Noncurrent accrued environmental remediation	2,311	2,926
Other noncurrent liabilities	8,618	7,951
Total liabilities	1,711,215	1,761,412
Commitments and contingencies (Note 15)
Mezzanine Capital
Subsidiary Series A Preferred Units (82,400 units issued and outstanding at June 30, 2020 and 30,058 units issued and outstanding at December 31, 2019)	78,563	27,450
Partners' Capital
Series A Preferred Units (300,000 units issued and outstanding at June 30, 2020 and December 31, 2019)	307,866	293,616
Common limited partner capital (43,543,056 units issued and outstanding at June 30, 2020 and 45,318,866 units issued and outstanding at December 31, 2019)	488,858	305,550
Noncontrolling interest		186,070
Total partners' capital	796,724	785,236
Total liabilities, mezzanine capital and partners' capital	$ 2,586,502	$ 2,574,098

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Jun. 30, 2020	Dec. 31, 2019
Subsidiary Series A preferred unitholders, issued	300,000	300,000
Subsidiary Series A preferred unitholders, outstanding	300,000	300,000
Common limited partner capital (in shares), issued	43,543,056	45,318,866
Common limited partner capital (in shares), outstanding	43,543,056	45,318,866
Mezzanine Capital
Subsidiary Series A preferred unitholders, issued	82,400	30,058
Subsidiary Series A preferred unitholders, outstanding	82,400	30,058

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Total revenues		$ 92,007	$ 99,686	$ 196,910	$ 231,094
Costs and expenses:
Cost of natural gas and NGLs		6,088	11,571	14,313	43,330
Operation and maintenance		21,152	24,318	42,963	48,540
General and administrative		12,786	10,565	29,347	28,950
Depreciation and amortization		29,630	26,837	59,296	54,601
Transaction costs		1,207	96	1,218	2,433
Gain on asset sales, net		(281)	(287)	(166)	(1,248)
Long-lived asset impairment		654	70	4,475	45,021
Total costs and expenses		71,236	73,170	151,446	221,627
Other income (expense)		276	83	(151)	292
Interest expense		(21,990)	(22,343)	(45,818)	(45,085)
Gain on early extinguishment of debt		54,235		54,235	0
Income (loss) before income taxes and income (loss) from equity method investees		53,292	4,256	53,730	(35,326)
Income tax benefit (expense)		389	(1,149)	402	(1,406)
Income (loss) from equity method investees		3,040	(79)	6,351	(520)
Net income (loss)		56,721	3,028	60,483	(37,252)
Net income (loss) attributable to noncontrolling interest		(1,393)	(1,341)	(3,274)	(26,911)
Net income (loss) attributable to limited partners		58,114	4,369	63,757	(10,341)
Series A Preferred Units
Costs and expenses:
Net income (loss) attributable to limited partners		7,125	7,125	14,250	14,250
Series A Preferred Units | Subsidiaries
Costs and expenses:
Net income (loss) attributable to limited partners		1,397		2,342
Common Units
Costs and expenses:
Net income (loss) attributable to limited partners		$ 49,592	$ (2,756)	$ 47,165	$ (24,591)
Income (Loss) per limited partner unit:
Basic (in dollars per share)		$ 1.11	$ (0.06)	$ 1.05	$ (0.54)
Diluted (in dollars per share)		$ 1.06	$ (0.06)	$ 1.02	$ (0.54)
Weighted-average limited partner units outstanding:
Basic (shares)	[1]	44,650	45,319	44,985	45,319
Diluted (shares)		46,737	45,319	46,323	45,319
Natural Gas, Gathering, Transportation, Marketing and Processing
Revenues:
Total revenues		$ 73,911	$ 75,107	$ 157,703	$ 162,071
Oil and Condensate
Revenues:
Total revenues		10,683	18,291	24,463	56,219
Product and Service, Other
Revenues:
Total revenues		$ 7,413	$ 6,288	$ 14,744	$ 12,804
[1]	As a result of the GP Buy-In Transaction, our historical results are those of Summit Investments. The number of common units of 45.3 million represents those of Summit Investments and has been used for the earnings per unit calculations presented herein.

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	Partners' Capital	Partners' CapitalSeries A Preferred Units	Noncontrolling InterestSeries A Preferred Units	Noncontrolling InterestCommon Noncontrolling Interest
Beginning balance at Dec. 31, 2018	$ 1,391,567	$ 543,479		$ 293,616	$ 554,472
Net income (loss)	(40,280)	(21,835)		7,125	(25,570)
Net cash distributions to SMLP unitholders	(27,374)				(27,374)
Unit-based compensation	2,526				2,526
Effect of common unit issuances under SMLP LTIP		(2,387)			2,387
Tax withholdings and associated payments on vested SMLP LTIP awards	(2,524)				(2,524)
Conversion of noncontrolling interest related to cancellation of subsidiary incentive distribution rights		48,203			(48,203)
Ending balance at Mar. 31, 2019	1,323,915	567,460		300,741	455,714
Net income (loss)	3,028	(2,756)		7,125	(1,341)
Net cash distributions to SMLP unitholders	(28,076)			(14,250)	(13,826)
Net cash distributions to Energy Capital Partners	(68,984)	(68,984)
Unit-based compensation	1,393				1,393
Effect of common unit issuances under SMLP LTIP		(40)			40
Tax withholdings and associated payments on vested SMLP LTIP awards	(93)				(93)
Ending balance at Jun. 30, 2019	1,231,183	495,680		293,616	441,887
Beginning balance at Dec. 31, 2019	785,236	305,550		293,616	186,070
Net income (loss)	2,817	(2,427)		7,125	(1,881)
Net cash distributions to SMLP unitholders	(6,037)				(6,037)
Unit-based compensation	2,723				2,723
Effect of common unit issuances under SMLP LTIP		(2,322)			2,322
Tax withholdings and associated payments on vested SMLP LTIP awards	(984)				(984)
Ending balance at Mar. 31, 2020	783,755	300,801		300,741	182,213
Net income (loss)	55,324	49,592	$ 2,375	4,750	(1,393)
Unit-based compensation	1,846	515			1,331
Tax withholdings and associated payments on vested SMLP LTIP awards	(62)	(28)			(34)
GP Buy-In Transaction assumption of noncontrolling interest in SMLP		182,117	305,491	$ (305,491)	$ (182,117)
Repurchase of common units under GP Buy-In Transaction	(44,078)	(44,078)
Other	(61)	(61)
Ending balance at Jun. 30, 2020	$ 796,724	$ 488,858	$ 307,866

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income (loss)	$ 60,483	$ (37,252)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	59,766	55,353
Noncash lease expense	1,557	1,530
Amortization of debt issuance costs	3,136	3,121
Unit-based and noncash compensation	4,569	4,079
(Income) loss from equity method investees	(6,351)	520
Distributions from equity method investees	12,749	18,217
Gain on asset sales, net	(166)	(1,248)
Gain on early extinguishment of debt	(54,235)	0
Long-lived asset impairment	4,475	45,021
Changes in operating assets and liabilities:
Accounts receivable	20,219	13,237
Trade accounts payable	1,411	(1,464)
Accrued expenses	(8)	(11,768)
Deferred revenue, net	5,500	2,007
Ad valorem taxes payable	(2,170)	(3,265)
Accrued interest	(609)	124
Accrued environmental remediation, net	(545)	(1,001)
Other, net	(4,410)	(2,637)
Net cash provided by operating activities	105,371	84,574
Cash flows from investing activities:
Capital expenditures	(27,426)	(111,092)
Proceeds from asset sale (net of cash of $1,475 for the period ended June 30, 2019)	0	89,761
Distribution from equity method investment	0	7,252
Investment in equity method investee	(79,728)	(5,921)
Other, net	217	(160)
Net cash used in investing activities	(106,937)	(20,160)
Cash flows from financing activities:
Net cash distributions to noncontrolling interest SMLP unitholders	(6,037)	(41,200)
Net cash distributions to Energy Capital Partners	0	(68,984)
Borrowings under Revolving Credit Facility	90,000	233,000
Repayments on Revolving Credit Facility	(34,000)	(126,000)
Repayments on SMP Holdings term loan	(6,300)	(53,750)
Repurchase of Senior Notes	(76,707)	0
Proceeds from issuance of Series A preferred units, net of costs	48,710	0
Borrowings under ECP Loans	35,000	0
Purchase of common units in GP Buy-In Transaction	(41,778)	0
Debt issuance costs	(1,080)	(229)
Proceeds from asset sale	288	0
Other, net	(1,833)	(3,532)
Net cash provided by (used in) financing activities	6,263	(74,945)
Net change in cash, cash equivalents and restricted cash	4,697	(10,531)
Cash, cash equivalents and restricted cash, beginning of period	36,922	16,173
Cash, cash equivalents and restricted cash, end of period	41,619	5,642
Supplemental cash flow disclosures:
Cash interest paid	44,073	43,683
Less capitalized interest	819	4,361
Interest paid (net of capitalized interest)	43,254	39,322
Cash paid for taxes	0	150
Noncash investing and financing activities
Capital expenditures in trade accounts payable (period-end accruals)	12,442	22,051
Warrant issuance for GP Buy-In Transaction	2,300	0
Asset contribution to an equity method investment	0	23,643
Series A Preferred Units
Cash flows from financing activities:
Distributions to unitholders	0	(14,250)
ASC Topic 842
Noncash investing and financing activities
Right-of-use assets relating to ASC Topic 842	$ 0	$ 5,448

UNAUDITED CONDENSED CONSOLIDA_6

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Statement Of Cash Flows [Abstract]
Net of cash	$ 1,475
Cash and cash equivalents	5,642
Restricted cash	0
Total cash, cash equivalents and restricted cash	$ 5,642

ORGANIZATION, BUSINESS OPERATIO

ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	1. ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION Organization. SMLP, a Delaware limited partnership, was formed in May 2012 and began operations in October 2012. SMLP is a value-oriented limited partnership focused on developing, owning and operating midstream energy infrastructure assets that are strategically located in unconventional resource basins, primarily shale formations, in the continental United States. Our business activities are conducted through various operating subsidiaries, each of which is owned or controlled by our wholly owned subsidiary holding company, Summit Holdings, a Delaware limited liability company. References to the "Partnership," "we," or "our" refer collectively to SMLP and its subsidiaries. On May 3, 2020, the Partnership entered into a Purchase Agreement (the “Purchase Agreement”) with affiliates of Energy Capital Partners II, LLC, a Delaware limited liability company (“ECP”). On May 28, 2020 (the “Closing Date”), the transactions contemplated by the Purchase Agreement closed. Pursuant to the Purchase Agreement, the Partnership acquired (i) all the outstanding limited liability company interests of Summit Midstream Partners, LLC, a Delaware limited liability company (“Summit Investments”), which is the sole member of Summit Midstream Partners Holdings, LLC, a Delaware limited liability company (“SMP Holdings”), which in turn owns (a) 34,604,581 common units representing limited partner interests in the Partnership (the “common units”) pledged as collateral under the Term Loan Agreement, dated as of March 21, 2017, among SMP Holdings, as borrower, the lenders party thereto and Credit Suisse AG, Cayman Islands Branch, as Administrative Agent and Collateral Agent (the “SMPH Term Loan”), (b) 10,714,285 common units not pledged as collateral under the SMPH Term Loan and (c) the right of SMP Holdings to receive the deferred purchase price obligation under the Contribution Agreement by and between the Partnership and SMP Holdings, dated February 25, 2016, as amended (the “Contribution Agreement”), and (ii) 5,915,827 common units held by SMLP Holdings, LLC, a Delaware limited liability company and an affiliate of ECP (“ECP Holdings”). The total purchase price under the Purchase Agreement was $35 million in cash and warrants to purchase up to 10 million common units (Refer to Note 11 for additional details). Pursuant to the Purchase Agreement, SMP Holdings continues to retain the liabilities stemming from the release of produced water from a produced water pipeline operated by Meadowlark Midstream Company, LLC that occurred near Williston, North Dakota and was discovered on January 6, 2015. We refer to the transactions contemplated by the Purchase Agreement as the “GP Buy-In Transaction.” As a result of the GP Buy-In Transaction, the Partnership now indirectly owns its General Partner. Following the closing of the GP Buy-In Transaction, the Partnership retired 16,630,112 common units it acquired under the Purchase Agreement that are not pledged as collateral under the SMPH Term Loan. The 34,604,581 common units that are pledged as collateral under the SMPH Term Loan are not considered outstanding with respect to voting and distributions under the Partnership Agreement so long as they are held by a subsidiary of the Partnership. Under GAAP, the GP Buy-In Transaction was deemed a transaction among entities under common control with a change in reporting entity. Although SMLP is the surviving entity for legal purposes, Summit Investments is the surviving entity for accounting purposes; therefore, the historical financial results included herein prior to the GP Buy-In Transaction are those of Summit Investments. Prior to the GP Buy-In Transaction, Summit Investments controlled SMLP and SMLP’s financial statements were consolidated into Summit Investments. Business Operations. We provide natural gas gathering, compression, treating and processing services as well as crude oil and produced water gathering services pursuant to primarily long-term, fee-based agreements with our customers. Our results are primarily driven by the volumes of natural gas that we gather, compress, treat and/or process as well as by the volumes of crude oil and produced water that we gather. We are the owner-operator of, or have significant ownership interests in, the following gathering and transportation systems: • Summit Utica, a natural gas gathering system operating in the Appalachian Basin, which includes the Utica and Point Pleasant shale formations in southeastern Ohio; • Ohio Gathering, a natural gas gathering system and a condensate stabilization facility operating in the Appalachian Basin, which includes the Utica and Point Pleasant shale formations in southeastern Ohio; • Polar and Divide, a crude oil and produced water gathering system and transmission pipeline operating in the Williston Basin, which includes the Bakken and Three Forks shale formations in northwestern North Dakota; • Bison Midstream, an associated natural gas gathering system operating in the Williston Basin, which includes the Bakken and Three Forks shale formations in northwestern North Dakota; • Niobrara G&P, an associated natural gas gathering and processing system operating in the DJ Basin, which includes the Niobrara and Codell shale formations in northeastern Colorado and southeastern Wyoming; • Summit Permian, an associated natural gas gathering and processing system operating in the northern Delaware Basin, which includes the Wolfcamp and Bone Spring formations, in southeastern New Mexico; • Double E, a 1.35 Bcf/d natural gas transmission pipeline that is under development and will provide transportation service from multiple receipt points in the Delaware Basin to various delivery points in and around the Waha Hub in Texas; • Grand River, a natural gas gathering and processing system operating in the Piceance Basin, which includes the Mesaverde formation and the Mancos and Niobrara shale formations in western Colorado; • DFW Midstream, a natural gas gathering system operating in the Fort Worth Basin, which includes the Barnett Shale formation in north-central Texas; and • Mountaineer Midstream, a natural gas gathering system operating in the Appalachian Basin, which includes the Marcellus Shale formation in northern West Virginia. Other than our investments in Double E and Ohio Gathering, all of our business activities are conducted through wholly owned operating subsidiaries. Presentation and Consolidation. We prepare our unaudited condensed consolidated financial statements in accordance with GAAP as established by the FASB. 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 revenues and expenses and the disclosure of commitments and contingencies. Further, these estimates and other factors, including those outside of our control, such as the impact of lower commodity prices, may have a significant negative impact to our business, financial condition, results of operations and cash flows. Although management believes these estimates are reasonable, actual results could differ from its estimates. The accompanying consolidated financial statements were prepared using GAAP for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission. As permitted under those rules, certain information relating to the Company’s organization and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been appropriately condensed or omitted. Therefore, these consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 (“2019 Annual Report”). The Partnership believes the disclosures made are adequate to make the information presented not misleading. The consolidated financial statements contained in this report include all normal and recurring material adjustments that, in the opinion of management, are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented herein. Risks and Uncertainties. We are closely monitoring the impact of the outbreak of COVID-19 on all aspects of our business, including how it has impacted and will impact our customers, employees, supply chain and distribution network. While COVID-19 did not have a material adverse effect on our reported results for the first six months of 2020, we are unable to predict the ultimate impact that COVID-19 may have on our business, future results of operations, financial position or cash flows. Given the dynamic nature of the COVID-19 pandemic and related market conditions, we cannot reasonably estimate the period of time that these events will persist or the full extent of the impact they will have on our business. The full extent to which our operations may be impacted by the COVID-19 pandemic will depend largely on future developments, which are highly uncertain and cannot be accurately predicted, including changes in the severity of the pandemic, countermeasures taken by governments, businesses and individuals to slow the spread of the pandemic, and the ability of pharmaceutical companies to develop effective and safe vaccines and therapeutic drugs. Furthermore, the impacts of a potential worsening of global economic conditions and the continued disruptions to and volatility in the financial markets remain unknown .

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Except for the changes below, there have been no changes to our significant accounting policies since December 31, 2019. Cash, Cash Equivalents and Restricted Cash . We consider all highly liquid investments with an original maturity of three months or less to be cash equivalents. Cash that is held by a major bank and has restrictions on its availability to us is classified as restricted cash. The restricted cash balance of $5.0 million at June 30, 2020 is primarily associated with an ongoing customer dispute and became unrestricted in July 2020, when an agreement was reached in the dispute. In conjunction with that agreement, the parties have agreed to (1) request dismissal of relevant lawsuits and modify the relevant gathering agreement, (2) petition the court to release to DFW Midstream approximately $5.4 million held in the court’s registry, and (3) the customer’s payment of approximately $1.9 million to DFW Midstream in installment payments over the course of four months, beginning on September 1, 2020. The restricted cash balance of $27.4 million at December 31, 2019 is primarily related to cash amounts reserved for funding the construction of our Double E pipeline. See Note 12 for additional information. 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. Accounting standards that have or could possibly have a material effect on our financial statements are discussed below. Recently Adopted Accounting Pronouncements . We have recently adopted the following accounting pronouncement: • ASU No. 2018-13 Fair Value Measurement (“ASU 2018-13”). ASU 2018-13 updates the disclosure requirements on fair value measurements including new disclosures for the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU 2018-13 modifies existing disclosures including clarifying the measurement uncertainty disclosure. ASU 2018-13 removes certain existing disclosure requirements including the amount and reasons for transfers between Level 1 and Level 2 fair value measurements and the policy for the timing of transfer between levels. The adoption of ASU 2018-13 on January 1, 2020 did not have a material impact on our unaudited condensed consolidated financial statement disclosures. • ASU No. 2016-13 Financial Instruments – Credit Losses (“ASU 2016-13”). ASU 2016-13 requires the use of a current expected loss model for financial assets measured at amortized cost and certain off-balance sheet credit exposures. Under this model, entities will be required to estimate the lifetime expected credit losses on such instruments based on historical experience, current conditions, and reasonable and supportable forecasts. This amended guidance also expands the disclosure requirements to enable users of financial statements to understand an entity’s assumptions, models and methods for estimating expected credit losses. The changes are effective for annual and interim periods beginning after December 15, 2019, and amendments should be applied using a modified retrospective approach. The adoption of ASU 2016-13 on January 1, 2020 did not have a material impact on our unaudited condensed consolidated financial statements or disclosures. Accounting Pronouncements Pending Adoption . We have not yet adopted the following accounting pronouncement as of June 30, 2020: • ASU No. 2020-04 Reference Rate Reform (“ASU 2020-04”). ASU 2020-04 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform on financial reporting. The amendments in ASU 2020-04 are effective as of March 12, 2020 through December 31, 2022. We are currently evaluating the provisions of ASU 2020-04 to determine its impact on our unaudited condensed consolidated financial statements and disclosures.

REVENUE

REVENUE	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
REVENUE	3. REVENUE The majority of our revenue is derived from long-term, fee-based contracts with our customers, which include original terms of up to 25 years. We recognize revenue earned from fee-based gathering, compression, treating and processing services in Gathering services and related fees. We also earn revenue in the Williston Basin and Permian Basin reporting segments from the sale of physical natural gas purchased from our customers under certain percent-of-proceeds arrangements. Under ASC Topic 606, these gathering contracts are presented net within Cost of natural gas and NGLs. We sell natural gas that we retain from certain customers in the Barnett Shale reporting segment to offset the power expenses of the electric-driven compression on the DFW Midstream system. We also sell condensate and NGLs retained from certain of our gathering services in the Piceance Basin and Permian Basin reporting segments. Revenues from the sale of natural gas and condensate are recognized in Natural gas, NGLs and condensate sales; 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, with the revenue component recognized in Other revenues. Performance obligations . The following table presents estimated revenue expected to be recognized during the remainder of 2020 and over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated MVC shortfall payments. We applied the practical expedient in paragraph 606-10-50-14 of ASC Topic 606 for certain arrangements that we consider optional purchases (i.e., there is no enforceable obligation for the customer to make purchases) and those amounts are therefore excluded from the table. 2020 2021 2022 2023 2024 Thereafter (In thousands) Gathering services and related fees $ 58,427 $ 102,127 $ 84,736 $ 66,693 $ 50,608 $ 57,721 Revenue by Category . In the following table, revenue is disaggregated by geographic area and major products and services. Ohio Gathering is excluded from the tables below due to equity method accounting. For more detailed information about reportable segments, see Note 4. Reportable Segments Three months ended June 30, 2020 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 11,538 $ 12,407 $ 5,228 $ 2,711 $ 26,222 $ 9,877 $ 5,928 $ 73,911 $ — $ 73,911 Natural gas, NGLs and condensate sales — 3,131 71 4,222 401 2,858 — 10,683 — 10,683 Other revenues — 2,776 993 126 1,096 1,778 — 6,769 644 7,413 Total $ 11,538 $ 18,314 $ 6,292 $ 7,059 $ 27,719 $ 14,513 $ 5,928 $ 91,363 $ 644 $ 92,007 Reportable Segments Six months ended June 30, 2020 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 18,500 $ 36,204 $ 12,083 $ 5,022 $ 53,411 $ 20,320 $ 12,163 $ 157,703 $ - $ 157,703 Natural gas, NGLs and condensate sales — 7,455 141 8,734 1,404 6,729 — 24,463 — 24,463 Other revenues — 5,918 2,027 313 2,161 3,038 — 13,457 1,287 14,744 Total $ 18,500 $ 49,577 $ 14,251 $ 14,069 $ 56,976 $ 30,087 $ 12,163 $ 195,623 $ 1,287 $ 196,910 Reportable Segments Three months ended June 30, 2019 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 7,591 $ 15,685 $ 4,021 $ 586 $ 30,555 $ 11,428 $ 5,897 $ 75,763 $ (656 ) $ 75,107 Natural gas, NGLs and condensate sales — 3,768 101 2,406 2,104 6,273 — 14,652 3,639 18,291 Other revenues — 2,670 1,034 49 945 1,646 — 6,344 (56 ) 6,288 Total $ 7,591 $ 22,123 $ 5,156 $ 3,041 $ 33,604 $ 19,347 $ 5,897 $ 96,759 $ 2,927 $ 99,686 Reportable Segments Six months ended June 30, 2019 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 15,086 $ 41,391 $ 7,745 $ 952 $ 62,395 $ 24,453 $ 12,094 $ 164,116 $ (2,045 ) $ 162,071 Natural gas, NGLs and condensate sales — 9,353 186 6,627 4,406 6,877 — 27,449 28,770 56,219 Other revenues — 5,578 2,041 81 2,083 3,302 — 13,085 (281 ) 12,804 Total $ 15,086 $ 56,322 $ 9,972 $ 7,660 $ 68,884 $ 34,632 $ 12,094 $ 204,650 $ 26,444 $ 231,094 Contract balances . Contract assets relate to our rights to consideration for work completed but not billed at the reporting date and consist of the estimated MVC shortfall payments expected from our customers and unbilled activity associated with contributions in aid of construction. Contract assets are transferred to trade receivables when the rights become unconditional. The following table provides information about contract assets from contracts with customers: June 30, 2020 December 31, 2019 (In thousands) Contract assets, beginning of period $ 3,902 $ 8,755 Additions 15,074 18,077 Transfers out (1,876 ) (22,930 ) Contract assets, end of period $ 17,100 $ 3,902 As of June 30, 2020, receivables with customers totaled $56.5 million and contract assets totaled $17.1 million which were included in the Accounts receivable caption on the unaudited condensed consolidated balance sheet. As of December 31, 2019, receivables with customers totaled $90.4 million and contract assets totaled $3.9 million which were included in the Accounts receivable caption on the unaudited condensed consolidated balance sheet. Contract liabilities (deferred revenue) relate to the advance consideration received from customers primarily for contributions in aid of construction. We recognize contract liabilities under these arrangements in revenue over the contract period. For the three months ended June 30, 2020 and 2019, we recognized $2.3 million and $2.7 million of gathering services and related fees which were included in the contract liability balance as of the beginning of the period. For the six months ended June 30, 2020 and 2019, we recognized $4.7 million and $5.4 million of gathering services and related fees which were included in the contract liability balance as of the beginning of the period. See Note 8 for additional details.

SEGMENT INFORMATION

SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	4. SEGMENT INFORMATION As of June 30, 2020, our reportable segments are: • the Utica Shale, which is served by Summit Utica; • Ohio Gathering, which includes our ownership interest in OGC and OCC; • the Williston Basin, which is served by Polar and Divide, Bison Midstream and Meadowlark Midstream; • the DJ Basin, which is served by Niobrara G&P; • the Permian Basin, which is served by Summit Permian; • the Piceance Basin, which is served by Grand River; • the Barnett Shale, which is served by DFW Midstream; and • the Marcellus Shale, which is served by Mountaineer Midstream. U ntil March 22, 2019, we owned Tioga Midstream, a crude oil, produced water and associated natural gas gathering system operating in the Williston Basin. Until December 1, 2019, we owned certain assets in the Red Rock Gathering system operating in the Piceance Basin. Refer to Note 1 6 to the unaudited condensed consolidated financial statements for details on the sale of Tioga Midstream and on the sale of certain assets in the Red Rock Gathering system . Each of our reportable segments provides midstream services in a specific geographic area. Our reportable segments reflect the way in which we internally report the financial information used to make decisions and allocate resources in connection with our operations. The Ohio Gathering reportable segment includes our investment in Ohio Gathering. Income or loss from equity method investees, as reflected on the unaudited condensed consolidated statements of operations, relates to Ohio Gathering and is recognized and disclosed on a one-month lag (see Note 7). For the three and six months ended June 30, 2020, other than the investment activity described in Note 7, Double E did not have any results of operations given that the Double E Project is currently under development. The Double E Project is expected to be operational in the third quarter of 2021. Corporate and Other represents those results that are: (i) not specifically attributable to a reportable segment; (ii) not individually reportable (such as Double E); or (iii) that have not been allocated to our reportable segments for the purpose of evaluating their performance, including certain general and administrative expense items, certain natural gas and crude oil marketing services, construction management fees related to the Double E Project and transaction costs. Assets by reportable segment follow. June 30, 2020 December 31, 2019 (In thousands) Assets (1): Utica Shale $ 210,592 $ 206,368 Ohio Gathering 269,504 275,000 Williston Basin 453,327 452,152 DJ Basin 203,866 205,308 Permian Basin 169,710 185,708 Piceance Basin 605,786 631,140 Barnett Shale 357,824 350,638 Marcellus Shale 183,896 184,631 Total reportable segment assets 2,454,505 2,490,945 Corporate and Other 131,997 83,153 Total assets $ 2,586,502 $ 2,574,098 (1) At June 30, 2020, Corporate and Other included $113.6 million relating to our investment in Double E (included in the Investment in equity method investees caption of the unaudited condensed consolidated balance sheet). At December 31, 2019, Corporate and Other included $34.7 million relating to our investment in Double E. Revenues by reportable segment follow. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Revenues (1): Utica Shale $ 11,538 $ 7,591 $ 18,500 $ 15,086 Williston Basin 18,314 22,123 49,577 56,322 DJ Basin 6,292 5,156 14,251 9,972 Permian Basin 7,059 3,041 14,069 7,660 Piceance Basin 27,719 33,604 56,976 68,884 Barnett Shale 14,513 19,347 30,087 34,632 Marcellus Shale 5,928 5,897 12,163 12,094 Total reportable segments revenue 91,363 96,759 195,623 204,650 Corporate and Other 644 3,824 1,287 30,662 Eliminations — (897 ) — (4,218 ) Total revenues $ 92,007 $ 99,686 $ 196,910 $ 231,094 (1) Excludes revenues earned by Ohio Gathering due to equity method accounting. Counterparties accounting for more than 10% of total revenues were as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 Percentage of total revenues (1): Counterparty A - Piceance Basin 11 % 12 % 11 % 11 % Counterparty B - Williston Basin * 11 % * 10 % Counterparty C - Barnett Shale * 14 % * 12 % (1) Excludes revenues earned by Ohio Gathering due to equity method accounting. * Less than 10% Depreciation and amortization, including the amortization expense associated with our favorable gas gathering contracts as reported in Other revenues, by reportable segment follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Depreciation and amortization (1): Utica Shale $ 1,920 $ 1,923 $ 3,847 $ 3,831 Williston Basin 6,487 4,734 12,982 10,170 DJ Basin 1,502 464 3,029 1,263 Permian Basin 1,387 1,163 2,732 2,235 Piceance Basin 11,306 11,810 22,604 23,601 Barnett Shale (2) 4,023 4,167 8,055 8,497 Marcellus Shale 2,300 2,286 4,600 4,569 Total reportable segment depreciation and amortization 28,925 26,547 57,849 54,166 Corporate and Other 941 653 1,917 1,187 Total depreciation and amortization $ 29,866 $ 27,200 $ 59,766 $ 55,353 (1) Excludes depreciation and amortization recognized by Ohio Gathering due to equity method accounting. (2) Includes the amortization expense associated with our favorable gas gathering contracts as reported in Other revenues . Cash paid for capital expenditures by reportable segment follow. Six months ended June 30, 2020 2019 (In thousands) Cash paid for capital expenditures (1): Utica Shale $ 1,482 $ 1,065 Williston Basin 7,423 14,230 DJ Basin 8,428 50,373 Permian Basin 4,921 28,163 Piceance Basin 404 1,497 Barnett Shale (2) 869 (37 ) Marcellus Shale 430 108 Total reportable segment capital expenditures 23,957 95,399 Corporate and Other 3,469 15,693 Total cash paid for capital expenditures $ 27,426 $ 111,092 (1) Excludes cash paid for capital expenditures by Ohio Gathering due to equity method accounting. (2) For the six months ended June 30, 2019, the amount includes sales tax reimbursements of $1.1 million. During the six months ended June 30, 2019, Corporate and Other included cash paid of $0.3 million for corporate purposes; the remainder represents capital expenditures relating to the Double E Project. We assess the performance of our reportable segments based on segment adjusted EBITDA. We define segment adjusted EBITDA as total revenues less total costs and expenses; plus (i) other income excluding interest income, (ii) our proportional adjusted EBITDA for equity method investees, (iii) depreciation and amortization, (iv) adjustments related to MVC shortfall payments, (v) adjustments related to capital reimbursement activity, (vi) unit-based and noncash compensation, (vii) impairments, (viii) other noncash expenses or losses, less other noncash income or gains and (ix) restructuring expenses. We define proportional adjusted EBITDA for our equity method investees as the product of (i) total revenues less total expenses, excluding impairments and other noncash income or expense items, and amortization for deferred contract costs; and (ii) our ownership interest in Ohio Gathering during the respective period. For the purpose of evaluating segment performance, we exclude the effect of Corporate and Other revenues and expenses, such as certain general and administrative expenses (including compensation-related expenses and professional services fees), certain natural gas and crude oil marketing services, transaction costs, interest expense and income tax expense or benefit from segment adjusted EBITDA. Segment adjusted EBITDA by reportable segment follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Reportable segment adjusted EBITDA Utica Shale $ 10,693 $ 6,640 $ 16,621 $ 12,833 Ohio Gathering 7,514 9,939 15,453 19,149 Williston Basin 12,727 16,650 28,919 35,384 DJ Basin 4,339 2,816 10,250 5,489 Permian Basin 1,828 (656 ) 3,409 (1,206 ) Piceance Basin 21,734 24,584 45,291 50,583 Barnett Shale 8,510 11,208 17,270 22,582 Marcellus Shale 4,888 4,635 10,208 9,777 Total of reportable segments' measures of profit $ 72,233 $ 75,816 $ 147,421 $ 154,591 A reconciliation of income or loss before income taxes and income or loss from equity method investees to total of reportable segments' measures of profit or loss follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Reconciliation of income (loss) before income taxes and income (loss) from equity method investees to total of reportable segments' measures of profit: Income (loss) before income taxes and income (loss) from equity method investees $ 53,292 $ 4,256 $ 53,730 $ (35,326 ) Add: Corporate and Other expense 9,533 8,255 21,610 24,905 Interest expense 21,990 22,343 45,818 45,085 Gain on early extinguishment of debt (54,235 ) — (54,235 ) — Depreciation and amortization 29,866 27,200 59,766 55,353 Proportional adjusted EBITDA for equity method investees 7,514 9,939 15,453 19,149 Adjustments related to MVC shortfall payments 2,291 3,533 (3,151 ) (666 ) Adjustments related to capital reimbursement activity (237 ) (1,046 ) (448 ) (1,761 ) Unit-based and noncash compensation 1,846 1,553 4,569 4,079 Gain on asset sales, net (281 ) (287 ) (166 ) (1,248 ) Long-lived asset impairment 654 70 4,475 45,021 Total of reportable segments' measures of profit $ 72,233 $ 75,816 $ 147,421 $ 154,591 Adjustments related to MVC shortfall payments recognize the earnings from MVC shortfall payments ratably over the term of the associated MVC (see Note 3). Contributions in aid of construction are recognized over the remaining term of the respective contract. We include adjustments related to capital reimbursement activity in our calculation of segment adjusted EBITDA to account for revenue recognized from contributions in aid of construction. Adjustments related to MVC shortfall payments by reportable segment follow. Three months ended June 30, 2020 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ 2,124 $ 167 $ — $ 2,291 Three months ended June 30, 2019 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ 2,081 $ — $ 1,452 $ 3,533 Six months ended June 30, 2020 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ (3,541 ) $ 390 $ — $ (3,151 ) Six months ended June 30, 2019 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ (3,468 ) $ (103 ) $ 2,905 $ (666 )

PROPERTY, PLANT, AND EQUIPMENT,

PROPERTY, PLANT, AND EQUIPMENT, NET	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
PROPERTY, PLANT, AND EQUIPMENT, NET	5. PROPERTY, PLANT AND EQUIPMENT, NET Details on property, plant and equipment follow. June 30, 2020 December 31, 2019 (In thousands) Gathering and processing systems and related equipment $ 2,193,200 $ 2,182,950 Construction in progress 76,189 78,716 Land and line fill 10,440 10,137 Other 60,414 54,595 Total 2,340,243 2,326,398 Less accumulated depreciation 484,354 443,909 Property, plant and equipment, net $ 1,855,889 $ 1,882,489 In March 2020, in connection with the cancellation of a compressor station project in the DJ Basin due to delays in customer drilling plans, we recorded an impairment charge of $3.6 million for the related soft project costs. In March 2019, certain events occurred which indicated that certain long-lived assets in the DJ Basin and Barnett Shale reporting segments could be impaired. Consequently, in the first quarter of 2019, we performed a recoverability assessment of certain assets within these reporting segments. Also in March 2019, in the DJ Basin we determined that certain processing plant assets related to our existing 20 MMcf/d plant would no longer be utilized due to our expansion plans for the Niobrara G&P system. Based on the results of the recoverability assessment and the conclusion that the carrying value was not fully recoverable, we recorded an impairment charge of $34.7 million related to these assets in the first quarter of 2019. In the first quarter of 2019, we determined that certain compressor station assets in the Barnett Shale were impaired and recorded an impairment charge of $10.2 million, comprised of a $9.7 impairment of fixed assets and a $0.5 million impairment of rights-of-way. Depreciation expense and capitalized interest follow. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Depreciation expense $ 21,664 $ 18,866 $ 43,362 $ 38,686 Capitalized interest 328 2,446 819 4,361

AMORTIZING INTANGIBLE ASSETS

AMORTIZING INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
AMORTIZING INTANGIBLE ASSETS	6. AMORTIZING INTANGIBLE ASSETS Details regarding our intangible assets, all of which are subject to amortization, follow: June 30, 2020 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (15,595 ) $ 8,600 Contract intangibles 278,448 (182,396 ) 96,052 Rights-of-way 157,202 (45,953 ) 111,249 Total intangible assets $ 459,845 $ (243,944 ) $ 215,901 December 31, 2019 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (15,125 ) $ 9,070 Contract intangibles 278,448 (169,549 ) 108,899 Rights-of-way 157,175 (42,866 ) 114,309 Total intangible assets $ 459,818 $ (227,540 ) $ 232,278 We recognized amortization expense in Other revenues as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Amortization expense – favorable gas gathering contracts $ (236 ) $ (363 ) $ (470 ) $ (752 ) We recognized amortization expense in costs and expenses as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Amortization expense – contract intangibles $ 6,423 $ 6,397 $ 12,847 $ 12,794 Amortization expense – rights-of-way 1,543 1,574 3,087 3,121 The estimated aggregate annual amortization expected to be recognized for the remainder of 2020 and each of the four succeeding fiscal years follows. Intangible assets (In thousands) 2020 $ 15,951 2021 28,209 2022 25,142 2023 25,088 2024 14,917

EQUITY METHOD INVESTMENTS

EQUITY METHOD INVESTMENTS	6 Months Ended
	Jun. 30, 2020
Equity Method Investments And Joint Ventures [Abstract]
EQUITY METHOD INVESTMENTS	7. EQUITY METHOD INVESTMENTS Double E In June 2019, we formed Double E in connection with the Double E Project. Effective June 26, 2019, Summit Permian Transmission, a wholly owned and consolidated subsidiary of the Partnership, and an affiliate of Double E’s foundation shipper (the “JV Partner”) During the six months ended June 30, 2020, we made cash investments of $79.7 million in the Double E Project. Double E is deemed to be a variable interest entity as defined in GAAP. As of the date of the Double E Agreement, Summit Permian Transmission wa s not deemed to be the primary beneficiary due to the JV Partner’s voting rights on significant matters. We account for our ownership interest in Double E as an equity method investment because we have significant influence over Double E. Our portion of Double E’s net assets, which was $ 113.6 million at June 3 0 , 20 20 , is reported under the caption Investment in equity method investees on the unaudited condensed consolidated balance sheet. For the three and six months ended June 30, 2020, other than the investment activity noted above, Double E did not have any results of operations given that the Double E Project is currently under development. Ohio Gathering Ohio Gathering owns and operates midstream infrastructure consisting of a liquids-rich natural gas gathering system, a dry natural gas gathering system and a condensate stabilization facility in the Utica Shale in southeastern Ohio. Ohio Gathering provides gathering services pursuant to primarily long-term, fee-based gathering agreements, which include acreage dedications. As of June 30, 2020 and December 31, 2019, our ownership interest in Ohio Gathering was 38.3% and 38.5%, respectively, and provided below is a reconciliation of the difference at June 30, 2020 between the amount at which our ownership interest in Ohio Gathering is carried to the amount of our underlying investment per Ohio Gathering's books and records (in thousands). Investment in Ohio Gathering, June 30, 2020 $ 269,504 June cash distributions 2,403 Basis difference 220,922 Investment in Ohio Gathering (Books and records), May 31, 2020 $ 492,829 As noted in our 2019 Annual Report, in December 2019 an impairment loss of long-lived assets was recognized by OCC which brought our investment in OCC to zero. As a result, we have not recorded our portion of OCC’s net loss for the three and six months ended June 30, 2020 in the Income (loss) from equity method investees caption of our unaudited condensed consolidated statements of operations. Summarized statements of operations information for OGC and OCC follow (amounts represent 100% of investee financial information). Three months ended May 31, 2020 Three months ended May 31, 2019 OGC OCC OGC OCC (In thousands) Total revenues $ 27,334 $ 2,404 $ 35,262 $ 2,073 Total operating expenses 24,045 2,069 26,336 2,691 Net income (loss) 3,289 335 8,926 (619 ) Six months ended May 31, 2020 Six months ended May 31, 2019 OGC OCC OGC OCC (In thousands) Total revenues $ 57,402 $ 5,131 $ 68,728 $ 4,339 Total operating expenses 49,795 32,924 51,823 5,664 Net income (loss) 7,600 (27,793 ) 16,898 (1,326 )

DEFERRED REVENUE

DEFERRED REVENUE	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
DEFERRED REVENUE	8. DEFERRED REVENUE A rollforward of current deferred revenue follows. Utica Shale Williston Basin DJ Basin Piceance Basin Barnett Shale Marcellus Shale Total current (In thousands) Current deferred revenue, January 1, 2020 $ 18 $ 1,933 $ 2,860 $ 7,014 $ 1,630 $ 38 $ 13,493 Additions 2 1,000 4,341 3,095 793 19 9,250 Less revenue recognized 9 967 2,483 3,092 819 19 7,389 Current deferred revenue, June 30, 2020 $ 11 $ 1,966 $ 4,718 $ 7,017 $ 1,604 $ 38 $ 15,354 A rollforward of noncurrent deferred revenue follows. Utica Shale Williston Basin DJ Basin Piceance Basin Barnett Shale Marcellus Shale Total noncurrent (In thousands) Noncurrent deferred revenue, January 1, 2020 $ 3 $ 3,634 $ 7,589 $ 17,710 $ 9,575 $ 198 $ 38,709 Additions 425 3,522 5,582 2,563 764 — 12,856 Less reclassification to current deferred revenue 2 967 4,341 3,095 793 19 9,217 Noncurrent deferred revenue, June 30, 2020 $ 426 $ 6,189 $ 8,830 $ 17,178 $ 9,546 $ 179 $ 42,348

DEBT

DEBT	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
DEBT	9. DEBT Debt consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Summit Holdings' variable rate senior secured Revolving Credit Facility (2.93% at June 30, 2020 and 4.55% at December 31, 2019) due May 2022 $ 733,000 $ 677,000 Summit Holdings' 8.00% senior secured term loan due March 2021 35,000 — Summit Holdings' 5.5% senior unsecured notes due August 2022 274,224 300,000 Less unamortized debt issuance costs (1) (1,252 ) (1,686 ) Summit Holdings' 5.75% senior unsecured notes due April 2025 393,765 500,000 Less unamortized debt issuance costs (1) (3,583 ) (5,015 ) SMP Holdings' variable rate senior secured term loan (7.00% at June 30, 2020 and 7.80% at December 31, 2019) due May 2022 155,200 161,500 Less unamortized debt issuance costs (1) (3,222 ) (3,974 ) Total debt 1,583,133 1,627,825 Less current portion 38,000 5,546 Total long-term debt $ 1,545,133 $ 1,622,279 (1) Issuance costs are being amortized over the life of the term loan and the Senior Notes. Revolving Credit Facility. Summit Holdings has a senior secured revolving credit facility which allows for revolving loans, letters of credit and swingline loans. The Revolving Credit Facility has a $1.25 billion borrowing capacity, matures in May 2022, and includes a $250.0 million accordion feature. As of June 30, 2020, SMLP and the Guarantor Subsidiaries fully and unconditionally and jointly and severally guarantee, and pledge substantially all of their assets in support of, the indebtedness outstanding under the Revolving Credit Facility. Borrowings under the Revolving Credit Facility bear interest, at the election of Summit Holdings, at a rate based on the alternate base rate (as defined in the credit agreement) plus an applicable margin ranging from 0.75% to 1.75% or the adjusted Eurodollar rate, as defined in the credit agreement, plus an applicable margin ranging from 1.75% to 2.75%, with the commitment fee ranging from 0.30% to 0.50% in each case based on our relative leverage at the time of determination. At June 30, 2020, the applicable margin under LIBOR borrowings was 2.75%, the interest rate was 2.93% and the unused portion of the Revolving Credit Facility totaled $512.9 million, subject to a commitment fee of 0.50 % , after giving effect to the issuance thereunder of a $ million outstanding but undrawn irrevocable standby letter of credit . Based on covenant limits, our available borrowing capacity under the Revolving Credit Facility as of June 30 , 2020 was approximately $ million. See Note 1 5 for additional information on our letter of credit. As of June 30, 2020, we had As of and during the six months ended June 30, 2020, we were in compliance with the Revolving Credit Facility's financial covenants. There were Summit Holdings Term Loans . On May 28, 2020, in connection with the closing of the GP Buy-In Transaction, Summit Holdings entered into (i) a Term Loan Credit Agreement (the “ECP NewCo Term Loan Credit Agreement”), with SMP TopCo, LLC, a Delaware limited liability company and affiliate of ECP (“ECP NewCo”), as lender and administrative agent, and Mizuho Bank (USA), as collateral agent (“Mizuho”), in a principal amount of $28.2 million (the “ECP NewCo Loan”), and (ii) a Term Loan Credit Agreement (the “ECP Holdings Term Loan Credit Agreement” and together with the ECP NewCo Term Loan Credit Agreement, the “ECP Term Loan Credit Agreements”), with ECP Holdings, as lender, and ECP NewCo, as administrative agent and Mizuho, as collateral agent, in a principal amount of $6.8 million (the “ECP Holdings Loan” and together with the ECP NewCo Loan, the “ECP Loans”). The ECP Loans mature on March 31, 2021 and are included in the current portion of long-term debt. The ECP Loans under each ECP Term Loan Credit Agreement bear interest at a rate of 8.00% per annum, with the interest expense due at maturity of the ECP Loans. Also on May 28, 2020 and in connection with the GP Buy-In Transaction, Summit Holdings entered into (i) in connection with the ECP NewCo Term Loan Credit Agreement, a Guarantee and Collateral Agreement (the “ECP NewCo Guarantee”), with the Partnership, the subsidiary guarantors listed therein and Mizuho and (ii) in connection with the ECP Holdings Term Loan Credit Agreement, a Guarantee and Collateral Agreement (the “ECP Holdings Guarantee” and together with the ECP NewCo Guarantee, the “ECP Term Loan Guarantees”), with the Partnership, the subsidiary guarantors listed therein and Mizuho. Pursuant to the ECP Term Loan Guarantees, the obligations under each of the ECP Term Loan Credit Agreements are generally (i) guaranteed by the Partnership and each subsidiary of Summit Holdings that guarantees the obligations under the Revolving Credit Facility, as and to the same extent as such guarantors guarantee the obligations under the Revolving Credit Facility and (ii) secured by a first priority lien on and security interest in all property on which a first priority lien and security interest secures the obligations under the Revolving Credit Facility, in each case, on the terms and subject to the conditions set forth in the ECP Term Loan Credit Agreements. The ECP Term Loan Credit Agreements each contain affirmative and negative covenants similar to those contained in the Revolving Credit Facility, that, among other things, limit or restrict the ability to (i) incur additional debt; (ii) incur certain liens on property; (iii) make investments; (iv) engage in certain mergers, consolidations, acquisitions or sales of assets; (v) declare or pay certain distributions with respect to equity interests; (vi) enter into certain transactions with any of its affiliates; (vii) enter into swap agreements and power purchase agreements; (viii) enter into certain leases that would cumulatively obligate payments in excess of $50 million over any 12-month period; and (ix) permit any Restricted Subsidiaries (as defined in the ECP Term Loan Credit Agreements) to sell certain industrial revenue bonds to certain parties without the consent of the administrative agent. In addition, the ECP Term Loan Credit Agreements contain maintenance financial covenants substantially similar to those contained in the Revolving Credit Facility, which will require Summit Holdings to maintain, beginning June 30, 2020: (a) a ratio of consolidated trailing 12-month earnings before interest, income taxes, depreciation and amortization (“EBITDA”) to net interest expense of not less than 2.50 to 1.00; (b) a ratio of total net indebtedness to consolidated trailing 12-month EBITDA of not more than 5.50 to 1.00; and (c) a ratio of first lien net indebtedness to consolidated trailing 12-month EBITDA of not more than 3.75 to 1.00. If any of the financial maintenance covenants contained in the Revolving Credit Facility are amended, modified or supplemented, the same financial maintenance covenant in each ECP Term Loan Credit Agreement will automatically be amended in the same manner. As of June 3 0 , 20 20 , the Partnership was in compliance with financial covenants of the ECP Loans ’ and t here were no defaults or events of default existing under either ECP Term Loan Credit Agreement as of June 30 , 20 20 . Senior Notes. In July 2014, Summit Holdings and its 100 owned finance subsidiary, Finance Corp. (together with Summit Holdings, the "Co-Issuers") co-issued $300.0 million of 5.5 senior unsecured notes maturing August 15, 2022 (the "5.5% Senior Notes" and, together with the 5.75 Senior Notes (defined below), the “Senior Notes”) as described in the 2019 Annual Report. In February 2017, the Co-Issuers completed a public offering of T he Guarantor Subsidiaries are 100% owned by a subsidiary of SMLP. The Guarantor Subsidiaries and SMLP fully and unconditionally and jointly and severally guarantee the Senior Notes. There are no significant restrictions on the ability of SMLP or Summit Holdings to obtain funds from its subsidiaries by dividend or loan. Finance Corp. has had no assets or operations since inception in 2013. We have no other independent assets or operations. At no time have the Senior Notes been guaranteed by the Co-Issuers. As of and during the six months ended June 30, 2020, we were in compliance with the covenants governing our Senior Notes and there were no defaults or events of default during the six months ended June 30, 2020. SMP Holdings Term Loan . On March 21, 2017, SMP Holdings entered into a senior secured term loan facility, the SMPH Term Loan, with a maturity date of May 15, 2022, pursuant to which term loans were made to SMP Holdings in the aggregate principal amount of $300.0 million. SMP Holdings became a subsidiary of the Partnership as a result of the GP Buy-In Transaction, and remains liable for the obligations under the SMPH Term Loan. The SMPH Term Loan bears interest at the Eurodollar Rate plus 6.00% or Alternate Base Rate plus 5.00% (each as defined in the SMPH Term Loan), in each case as elected by SMP Holdings in accordance with the SMPH Term Loan. The SMPH Term The SMPH Term Loan contains certain customary representations and warranties, affirmative covenants and events of default, including, but not limited to, payment defaults, breaches of representations and warranties, covenant defaults, certain events of insolvency or bankruptcy, material judgments, certain events under ERISA, actual or asserted failures of any guaranty or security document supporting the SMPH Term Loan to be in full force and effect and changes of control. The obligations related to the SMPH Term Loan are (1) guaranteed by Summit Investments and (2) secured by the following collateral: (i) a perfected first-priority lien on, and pledge of, (A) all of the capital stock issued by SMP Holdings, (B) 34.6 million SMLP common units owned by SMP Holdings, (C) all of the equity interests owned by SMP Holdings in the General Partner, and (ii) substantially all other personal property of SMP Holdings. Loans under the SMPH Term Loan must be prepaid or there must be an offer to prepay the loans under the SMPH Term Loan under certain circumstances SMP Holdings is required to repay principal amounts outstanding under the SMPH Term Loan quarterly in an amount equal to 1.0% per annum of the original principal amount of the loans under the SMPH Term Loan. SMP Holdings’ current portion of long-term debt includes scheduled principal amortization. We were not required to make an excess cash flow payment on the SMPH Term Loan for the second quarter of 2020, and have not included an estimated excess cash flow amount in the current portion of long-term debt relating to the third and fourth quarter of 2020 and the first quarter of 2021 because the amount is not currently estimable given that the excess cash flow calculation is based on the occurrence of future events. On April 17, 2020, we entered into a derivative financial instrument to convert a portion of our variable rate SMPH Term Loan to a fixed rate debt consisting of a 1% LIBOR interest rate cap for a fee of $0.2 million (exclusive of the applicable bank margin charged by our lender) on a $125.0 million notional amount beginning April 30, 2020 and ending on April 30, 2022. We have not designated the interest rate cap for hedge accounting as defined by GAAP and recognized an unsettled gain of $0.1 million on the interest rate cap in the other income line item on our unaudited condensed consolidated statement of operations for the three and six month periods ended June 30, 2020. As of June 30, 2020, SMP Holdings was in compliance with the SMPH Term Loan’s financial covenants and there were no defaults or events of default existing under the SMPH Term Loan as of June 30, 2020. Repurchases. Subsequent to the GP Buy-In Transaction, the Partnership commenced a debt buyback program to repurchase our Senior Notes, which is ongoing. We repurchased $25.8 million of the outstanding $300 million aggregate principal amount of our 5.50% Senior Notes through June 30, 2020. The gain on early extinguishment of debt for the 5.50% Senior Notes during the three and six months ended June 30, 2020 totaled $9.2 million and is inclusive of a $0.1 million write off of debt issuance costs. We also repurchased $106.2 million of the outstanding $500 million aggregate principal amount of our 5.75% Senior Notes through June 30, 2020. The gain on early extinguishment of debt for the 5.75% Senior Notes during the three and six months ended June 30, 2020 totaled $45.1 million and is inclusive of a $1.0 million write off of debt issuance costs.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
FINANCIAL INSTRUMENTS	10. FINANCIAL INSTRUMENTS Concentrations of Credit Risk. Financial instruments that potentially subject us to concentrations of credit risk consist of cash and cash equivalents, restricted cash and accounts receivable. We maintain our cash and cash equivalents and restricted 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 amounts due for the gathering, compression, treating and processing services we provide to our customers and also the sale of natural gas liquids resulting from our processing services. 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 or other forms of credit assurance for receivables from counterparties that are judged to have substandard credit, unless the credit risk can otherwise be mitigated. Our top Fair Value. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable, trade accounts payable and ECP Loans reported on the unaudited condensed consolidated balance sheet approximates fair value due to their short-term maturities. A summary of the estimated fair value of our debt financial instruments follows. June 30, 2020 December 31, 2019 Carrying value Estimated fair value (Level 2) Carrying value Estimated fair value (Level 2) (In thousands) Summit Holdings 5.5% principal) $ 272,973 $ 180,531 $ 298,314 $ 266,750 Summit Holdings 5.75% principal) 390,183 211,977 494,985 382,708 The carrying values on the balance sheet of the Revolving Credit Facility and the SMPH Term Loan are their fair values due their floating interest rates. The fair value for the Senior Notes is based on an average of nonbinding broker quotes as of June 30, 2020 and December 31, 2019. The use of different market assumptions or valuation methodologies may have a material effect on the estimated fair value of the Senior Notes.

PARTNERS' CAPITAL AND MEZZANINE

PARTNERS' CAPITAL AND MEZZANINE CAPITAL	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
PARTNERS' CAPITAL AND MEZZANINE CAPITAL	11. PARTNERS' CAPITAL AND MEZZANINE CAPITAL A rollforward of the number of common limited partner units follows. Common Units Units, December 31, 2019 (1) 45,318,866 Net units issued under the SMLP LTIP 308,364 Impact of GP Buy-In Transaction (2,084,174 ) Units, June 30, 2020 (1) 43,543,056 (1) As a result of the GP Buy-In Transaction, the recast of the historical financial statements resulted in a recasted common limited partner unit count of 45.3 million units at December 31, 2019. Prior to the GP Buy-In Transaction, the common limited partner unit count was 93.5 million units at December 31, 2019, and after adjusting these 93.5 million units for the effect of 1.2 million units issued through June 30, 2020 for the SMLP LTIP, and the GP Buy-In Transaction’s repurchase of 34.6 million units pledged under the Term Loan B, the 10.7 million units not pledged under the Term Loan B, and the 5.9 million units owned by ECP, the common limited partner unit count would have been an otherwise identical 43.5 million common limited partner units at June 30, 2020. GP Buy-In Transaction. The purchase price for the common units reflected in the unaudited condensed consolidated statement of partners’ capital for the six months ended June 30, 2020 is comprised of the (i) the $35.0 million cash payment to ECP, (ii) the $2.3 million fair value for the issuance of 10,000,000 warrants, (iii) and $6.8 million of advisory fees and other direct costs related to closing the GP Buy-In Transaction. Series A Preferred Units. In 2017, we issued 300,000 Series A Preferred Units representing limited partner interests in the Partnership at a price to the public of $1,000 per unit as described in the 2019 Annual Report. In connection with the GP Buy-In Transaction, the Partnership suspended its distributions to holders of its Series A Preferred Units, commencing with respect to the quarter ending March 31, 2020. On June 18, 2020, the Partnership, commenced an offer to exchange any and all of its Series A Preferred Units for newly issued common units (the “Exchange Offer”). As of June 30, 2020, the Exchange Offer was still pending. See Note 17 for additional details on the Exchange Offer. Subsidiary Series A Preferred Units. In December 2019, we issued 30,000 Subsidiary Series A Preferred Units representing limited partner interests in Permian Holdco at a price of $1,000 per unit as described in the 2019 Annual Report. During the six months ended June 30, 2020, we issued an additional 50,000 Subsidiary Series A Preferred Units representing limited partner interests in Permian Holdco at a price of $1,000 per unit. We used the net proceeds of $48.7 million (after deducting underwriting discounts and offering expenses) to fund our share of capital expenses associated with the Double E Project. The proceeds associated with the issuance of Subsidiary Series A Preferred Units are classified as restricted cash on the accompanying unaudited condensed consolidated balance sheets in accordance with the underlying agreement with TPG Energy Solutions Anthem, L.P. until the related funding is used for the Double E Project. Warrants. On May 28, 2020 and in connection with the GP Buy-In Transaction, the Partnership issued (i) a Warrant to purchase up to 8,059,609 common units to ECP NewCo (the “ECP NewCo Warrant”) and (ii) a Warrant to purchase up to 1,940,391 common units to ECP Holdings (the “ECP Holdings Warrant” and together with the ECP NewCo Warrant, the “ECP Warrants”). The exercise price under the ECP Warrants is $1.023 per common unit. The Partnership may issue a maximum of 10,000,000 common units under the ECP Warrants. The ECP Warrants also provide that the Partnership will file a registration statement to register the common units issuable upon exercise of the ECP Warrants no later than 90 days following the Closing Date and use commercially reasonable efforts to cause such registration statement to become effective. Upon exercise of the ECP Warrants, each of ECP NewCo and ECP Holdings may receive, at its election: (i) a number of common units equal to the number of common units for which the ECP Warrant is being exercised, if exercising the ECP Warrant by cash payment of the exercise price; (ii) a number of common units equal to the product of the number of common units being exercised multiplied by (a) the difference between the average of the daily volume-weighted average price (“VWAP”) of the common units on the New York Stock Exchange (the “NYSE”) on each of the three trading days prior to the delivery of the notice of exercise (the “VWAP Average”) and the exercise price (the “VWAP Difference”), divided by (b) the VWAP Average; and/or (iii) an amount in cash, to the extent that the Partnership’s leverage ratio would be at least 0.5x less than the maximum applicable ratio set forth in the Revolving Credit Facility, equal to the product of (a) the number of common units exercised and (b) the VWAP Difference, subject to certain adjustments under the ECP Warrants . The ECP Warrants are subject to standard anti-dilution adjustments for stock dividends, stock splits and recapitalizations and are exercisable at any time after the Closing Date and on or before the third anniversary of the Closing Date. Upon exercise of the ECP Warrants, the proceeds to the holders of the ECP Warrants, whether in the form of cash or common units, will be capped at $2.00 per common unit above the exercise price. At issuance we valued the ECP Warrants at $2.3 million using a Black-Scholes model and account for the ECP Warrants as a liability instrument. At June 30, 2020, the ECP Warrants were valued at $2.3 million. SMLP General Partner and Incentive Distribution Rights (“IDR”) Exchange. In March 2019, and prior to the GP Buy-In Transaction, a subsidiary of Summit Investments cancelled its IDR agreement with SMLP and converted its 2% economic general partner interest to a non-economic general partner interest in exchange for 8,750,000 SMLP common units. This exchange is reflected in the Consolidated Statements of Partners’ Capital as a reduction to noncontrolling interest and an increase to Partners’ Capital. Cash Distributions Paid and Declared. Prior to the GP Buy-In Transaction, SMLP paid the following per-unit distributions during the three and six months ended June 30 (All payments represent per-unit distributions based on the SMLP common units outstanding prior to the GP Buy-In Transaction): Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 Per-unit distributions to unitholders $ — $ 0.2875 $ 0.125 $ 0.8625 In connection with the GP Buy-In Transaction, With respect to our Subsidiary Series A Preferred Units relating to the three and six months ended June 30, 2020, we declared a payment-in-kind ("PIK") of the quarterly distribution, which resulted in the issuance of 490 Subsidiary Series A Preferred Units and 1,397 Subsidiary Series A Preferred Units, respectively. This PIK amount equates to a distribution of $30.7320 and $17.2579 per Subsidiary Series A Preferred Unit for the three and six months ended June 30, 2020, respectively, or $70 on an annualized basis. In addition, we issued approximately 38 Subsidiary Series A Preferred Units related to the remaining undrawn commitment (as defined in the underlying agreement with TPG Energy Solutions Anthem, L.P.) as of and for the six months ended June 30, 2020.

EARNINGS PER UNIT

EARNINGS PER UNIT	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
EARNINGS PER UNIT	12. EARNINGS PER UNIT The following table details the components of EPU. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net income (loss) among limited partner interests: Net income (loss) attributable to limited partners $ 58,114 $ 4,369 $ 63,757 $ (10,341 ) Less net income attributable to Series A Preferred Units 7,125 7,125 14,250 14,250 Less net income attributable to Subsidiary Series A Preferred Units 1,397 — 2,342 — Net income (loss) attributable to common limited partners $ 49,592 $ (2,756 ) $ 47,165 $ (24,591 ) Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic (1) 44,650 45,319 44,985 45,319 Effect of nonvested phantom units 2,087 — 1,338 — Weighted-average common units outstanding – diluted 46,737 45,319 46,323 45,319 Income (Loss) per limited partner unit: Common unit – basic $ 1.11 $ (0.06 ) $ 1.05 $ (0.54 ) Common unit – diluted $ 1.06 $ (0.06 ) $ 1.02 $ (0.54 ) Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 4,139 — 3,014 17 (1) As a result of the GP Buy-In Transaction, our historical results are those of Summit Investments. The number of common units of 45.3 million represents those of Summit Investments and has been used for the earnings per unit calculations presented herein. As discussed in Note 9, the SMPH Term Loan is secured by 34.6 million SMLP common units owned by SMP Holdings. These common units are not included in the calculation of EPU because they are not deemed contingently issuable under GAAP.

UNIT-BASED AND NONCASH COMPENSA

UNIT-BASED AND NONCASH COMPENSATION	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
UNIT-BASED AND NONCASH COMPENSATION	13. UNIT-BASED AND NONCASH COMPENSATION SMLP Long-Term Incentive Plan. The SMLP LTIP provides for equity awards to eligible officers, employees, consultants and directors. Items to note: • In March 2020, we granted 3,811,301 phantom units and associated distribution equivalent rights to employees in connection with our annual incentive compensation award cycle. These awards had a grant date fair value of $0.55 and vest ratably over a three-year • In March 2020, we also issued 549,450 common units to our three independent directors in connection with their annual compensation plan. • In June 2020, we issued 187,500 common units to three new independent directors in connection with their annual compensation plan. • During the six months ended June 30, 2020, 539,721 phantom units vested. • In March 2020, we increased the number of common units authorized under the SMLP LTIP to 15,000,000 common units and extended the term of the SMLP LTIP for 10 years. • As of June 30, 2020, approximately 6.7 common units remained available for future issuance under the SMLP LTIP.

RELATED-PARTY TRANSACTIONS

RELATED-PARTY TRANSACTIONS	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
RELATED-PARTY TRANSACTIONS	14. RELATED-PARTY TRANSACTIONS Acquisitions. See Notes 1 and 17 of the 2019 Annual Report.

LEASES, COMMITMENTS AND CONTING

LEASES, COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
LEASES, COMMITMENTS AND CONTINGENCIES	15. LEASES, COMMITMENTS AND CONTINGENCIES Leases. Right-of-Use (“ROU”) assets (included in the Property, plant and equipment, net caption on our unaudited condensed consolidated balance sheet) and lease liabilities (included in the Other current liabilities and Other noncurrent liabilities captions on our unaudited condensed consolidated balance sheet) follow: June 30, 2020 December 31, 2019 (In thousands) ROU assets Operating $ 4,996 $ 3,580 Finance 2,253 3,159 $ 7,249 $ 6,739 Lease liabilities, current Operating $ 1,659 $ 1,221 Finance 826 1,246 $ 2,485 $ 2,467 Lease liabilities, noncurrent Operating $ 4,120 $ 2,513 Finance 310 676 $ 4,430 $ 3,189 We recognize total lease expense incurred in general and administrative expenses. Lease expense related to operating leases, was as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Lease expense $ 937 $ 1,033 $ 1,890 $ 2,023 Environmental Matters. Although we believe that we are in material compliance with applicable environmental regulations, the risk of environmental remediation costs and liabilities are inherent in pipeline ownership and operation. Furthermore, we can provide no assurances that significant environmental remediation 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, except as noted below. In 2015, we learned of the rupture of a four-inch produced water gathering pipeline on the Meadowlark Midstream system near Williston, North Dakota. The incident, which was covered by insurance policies, was subject to maximum coverage of A rollforward of the Partnership’s undiscounted accrued environmental remediation liabilities follows. Total (In thousands) Accrued environmental remediation, January 1, 2020 $ 4,651 Payments made (545 ) Accrued environmental remediation, June 30, 2020 $ 4,106 As of June 30, 2020, we have recognized (i) a current liability for remediation effort expenditures expected to be incurred within the next 12 months and (ii) a noncurrent liability for estimated remediation expenditures and fines expected to be incurred subsequent to June 30, 2021. Each of these amounts represent our best estimate for costs expected to be incurred. Neither of these amounts has been discounted to its present value. Prior to the GP Buy-In Transaction, Summit Investments and SMP Holdings indemnified the Partnership for certain obligations and liabilities related to the incident. As a result of the GP Buy-In Transaction, the Partnership is no longer indemnified for these obligations by a third party. The U.S. Department of Justice issued grand jury subpoenas to the Partnership requesting certain materials related to the Meadowlark Midstream rupture. Based on information currently available to the Partnership, the Partnership believes a loss for claims and/or actions arising from the Meadowlark Midstream rupture is probable. Due to the complexity surrounding the resolution of the Meadowlark Midstream rupture, the Partnership is not able to reasonably estimate the extent of the Partnership’s loss for this matter, or to express an opinion regarding the ultimate outcome. Any such loss, if incurred, could be material . 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 or those arising in the normal course of business would not individually or in the aggregate have a material adverse effect on the Partnership's financial position or results of operations.

DISPOSITIONS AND RESTRUCTURING

DISPOSITIONS AND RESTRUCTURING	6 Months Ended
	Jun. 30, 2020
Business Combinations [Abstract]
DISPOSITIONS AND RESTRUCTURING	16. DISPOSITIONS AND RESTRUCTURING Tioga Midstream Disposition. In February 2019, Tioga Midstream, LLC, a subsidiary of SMLP, and certain affiliates of SMLP (collectively, “Summit”) entered into two Purchase and Sale Agreements (the “Tioga PSAs”) with Hess Infrastructure Partners LP and Hess North Dakota Pipelines LLC (collectively, “Hess Infrastructure”), pursuant to which Summit agreed to sell the Tioga Midstream system to Hess Infrastructure for a combined cash purchase price of $90 million, subject to adjustments as provided in the Tioga PSAs (the “Tioga Midstream Sale”). On March 22, 2019, Summit closed the Tioga Midstream Sale and recorded a gain on sale of $0.9 million based on the difference between the consideration received and the carrying value for Tioga Midstream at closing. The gain is included in the Gain on asset sales, net caption on the unaudited condensed consolidated statement of operations. The financial results of Tioga Midstream (a component of the Williston Basin reportable segment) are included in our unaudited condensed consolidated financial statements and footnotes for the period from January 1, 2019 through March 22, 2019. 2016 Drop Down. In 2016, SMLP acquired a controlling interest in OpCo, the entity which owns the 2016 Drop Down Assets. The net consideration paid and recognized in connection with the 2016 Drop Down (i) consisted of a cash payment to SMP Holdings of $360.0 million funded with borrowings under our Revolving Credit Facility and a $0.6 million working capital adjustment received in June 2016 and (ii) includes the Deferred Purchase Price Obligation payment due in 2020. As a result of the GP Buy-In Transaction (Refer to Note 1 for additional details), SMP Holdings transferred its right to receive payment of the Deferred Purchase Price Obligation under the Contribution Agreement. Under the Contribution Agreement, the Partnership is now required to pay the remaining consideration under the Contribution Agreement to its subsidiary, Summit Contribution Holdings, LLC, by January 15, 2022. Because this obligation is owed to the Partnership’s own subsidiary, the unaudited condensed consolidated balance sheet as of June 30, 2020 and December 31, 2019 reflects no liabilities associated with this obligation. Restructuring Activities. As of December 31, 2019, we had $3.3 million of unpaid employee severance costs related to 2019 restructuring initiatives that resulted in certain management, facility and organizational changes. During the three- and six-month periods ended June 30, 2020, our 2019 restructuring initiatives resulted in additional restructuring costs of $0.6 million and $3.3 million, respectively. We paid out $5.7 million of these 2019 restructuring costs during the six months ended June 30, 2020 and have a $0.9 million current liability for unpaid employee severance costs at June 30, 2020 related to these 2019 restructuring initiatives. The 2019 restructuring activities primarily consisted of employee-related costs and consulting costs in support of the restructuring initiatives. Restructuring costs are included within the General and administrative caption on the condensed consolidated statement of operations.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	17. SUBSEQUENT EVENTS We have evaluated subsequent events for recognition or disclosure in the unaudited condensed consolidated financial statements and no events have occurred that require recognition or disclosure, except for the following. The Exchange Offer expired on July 28, 2020 and the Partnership exchanged 62,816 Series A Preferred Units at a ratio of 200 common units per Series A Preferred Unit for a total of 12,563,200 common units, subject to applicable withholding taxes. Upon completion of the Exchange Offer, 237,184 Series A Preferred Units were not tendered and remain outstanding. Subsequent to June 30, 2020 and through August 6, 2020, we have repurchased approximately $5.9 million face value of Summit Holdings and Finance Corp 5.5% senior unsecured notes due August 2022 at a weighted average 34% discount for approximately $3.9 million in cash. On August 7, 2020, we repaid all amounts outstanding under the ECP Loans which included $35 million of principal and $0.6 million of accrued interest.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Cash and Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash . We consider all highly liquid investments with an original maturity of three months or less to be cash equivalents. Cash that is held by a major bank and has restrictions on its availability to us is classified as restricted cash. The restricted cash balance of $5.0 million at June 30, 2020 is primarily associated with an ongoing customer dispute and became unrestricted in July 2020, when an agreement was reached in the dispute. In conjunction with that agreement, the parties have agreed to (1) request dismissal of relevant lawsuits and modify the relevant gathering agreement, (2) petition the court to release to DFW Midstream approximately $5.4 million held in the court’s registry, and (3) the customer’s payment of approximately $1.9 million to DFW Midstream in installment payments over the course of four months, beginning on September 1, 2020. The restricted cash balance of $27.4 million at December 31, 2019 is primarily related to cash amounts reserved for funding the construction of our Double E pipeline. See Note 12 for additional information.
Recent Accounting Pronouncements	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. Accounting standards that have or could possibly have a material effect on our financial statements are discussed below. Recently Adopted Accounting Pronouncements . We have recently adopted the following accounting pronouncement: • ASU No. 2018-13 Fair Value Measurement (“ASU 2018-13”). ASU 2018-13 updates the disclosure requirements on fair value measurements including new disclosures for the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU 2018-13 modifies existing disclosures including clarifying the measurement uncertainty disclosure. ASU 2018-13 removes certain existing disclosure requirements including the amount and reasons for transfers between Level 1 and Level 2 fair value measurements and the policy for the timing of transfer between levels. The adoption of ASU 2018-13 on January 1, 2020 did not have a material impact on our unaudited condensed consolidated financial statement disclosures. • ASU No. 2016-13 Financial Instruments – Credit Losses (“ASU 2016-13”). ASU 2016-13 requires the use of a current expected loss model for financial assets measured at amortized cost and certain off-balance sheet credit exposures. Under this model, entities will be required to estimate the lifetime expected credit losses on such instruments based on historical experience, current conditions, and reasonable and supportable forecasts. This amended guidance also expands the disclosure requirements to enable users of financial statements to understand an entity’s assumptions, models and methods for estimating expected credit losses. The changes are effective for annual and interim periods beginning after December 15, 2019, and amendments should be applied using a modified retrospective approach. The adoption of ASU 2016-13 on January 1, 2020 did not have a material impact on our unaudited condensed consolidated financial statements or disclosures. Accounting Pronouncements Pending Adoption . We have not yet adopted the following accounting pronouncement as of June 30, 2020: • ASU No. 2020-04 Reference Rate Reform (“ASU 2020-04”). ASU 2020-04 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform on financial reporting. The amendments in ASU 2020-04 are effective as of March 12, 2020 through December 31, 2022. We are currently evaluating the provisions of ASU 2020-04 to determine its impact on our unaudited condensed consolidated financial statements and disclosures.
Basis of Presentation	Presentation and Consolidation. We prepare our unaudited condensed consolidated financial statements in accordance with GAAP as established by the FASB. 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 revenues and expenses and the disclosure of commitments and contingencies. Further, these estimates and other factors, including those outside of our control, such as the impact of lower commodity prices, may have a significant negative impact to our business, financial condition, results of operations and cash flows. Although management believes these estimates are reasonable, actual results could differ from its estimates. The accompanying consolidated financial statements were prepared using GAAP for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission. As permitted under those rules, certain information relating to the Company’s organization and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been appropriately condensed or omitted. Therefore, these consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 (“2019 Annual Report”). The Partnership believes the disclosures made are adequate to make the information presented not misleading. The consolidated financial statements contained in this report include all normal and recurring material adjustments that, in the opinion of management, are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented herein. Risks and Uncertainties. We are closely monitoring the impact of the outbreak of COVID-19 on all aspects of our business, including how it has impacted and will impact our customers, employees, supply chain and distribution network. While COVID-19 did not have a material adverse effect on our reported results for the first six months of 2020, we are unable to predict the ultimate impact that COVID-19 may have on our business, future results of operations, financial position or cash flows. Given the dynamic nature of the COVID-19 pandemic and related market conditions, we cannot reasonably estimate the period of time that these events will persist or the full extent of the impact they will have on our business. The full extent to which our operations may be impacted by the COVID-19 pandemic will depend largely on future developments, which are highly uncertain and cannot be accurately predicted, including changes in the severity of the pandemic, countermeasures taken by governments, businesses and individuals to slow the spread of the pandemic, and the ability of pharmaceutical companies to develop effective and safe vaccines and therapeutic drugs. Furthermore, the impacts of a potential worsening of global economic conditions and the continued disruptions to and volatility in the financial markets remain unknown .

REVENUE (Tables)

REVENUE (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
Schedule of Estimated Revenue Expected to be Recognized and MVC Shortfall Payments	The following table presents estimated revenue expected to be recognized during the remainder of 2020 and over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated MVC shortfall payments. We applied the practical expedient in paragraph 606-10-50-14 of ASC Topic 606 for certain arrangements that we consider optional purchases (i.e., there is no enforceable obligation for the customer to make purchases) and those amounts are therefore excluded from the table. 2020 2021 2022 2023 2024 Thereafter (In thousands) Gathering services and related fees $ 58,427 $ 102,127 $ 84,736 $ 66,693 $ 50,608 $ 57,721
Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments	Revenue by Category . In the following table, revenue is disaggregated by geographic area and major products and services. Ohio Gathering is excluded from the tables below due to equity method accounting. For more detailed information about reportable segments, see Note 4. Reportable Segments Three months ended June 30, 2020 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 11,538 $ 12,407 $ 5,228 $ 2,711 $ 26,222 $ 9,877 $ 5,928 $ 73,911 $ — $ 73,911 Natural gas, NGLs and condensate sales — 3,131 71 4,222 401 2,858 — 10,683 — 10,683 Other revenues — 2,776 993 126 1,096 1,778 — 6,769 644 7,413 Total $ 11,538 $ 18,314 $ 6,292 $ 7,059 $ 27,719 $ 14,513 $ 5,928 $ 91,363 $ 644 $ 92,007 Reportable Segments Six months ended June 30, 2020 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 18,500 $ 36,204 $ 12,083 $ 5,022 $ 53,411 $ 20,320 $ 12,163 $ 157,703 $ - $ 157,703 Natural gas, NGLs and condensate sales — 7,455 141 8,734 1,404 6,729 — 24,463 — 24,463 Other revenues — 5,918 2,027 313 2,161 3,038 — 13,457 1,287 14,744 Total $ 18,500 $ 49,577 $ 14,251 $ 14,069 $ 56,976 $ 30,087 $ 12,163 $ 195,623 $ 1,287 $ 196,910 Reportable Segments Three months ended June 30, 2019 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 7,591 $ 15,685 $ 4,021 $ 586 $ 30,555 $ 11,428 $ 5,897 $ 75,763 $ (656 ) $ 75,107 Natural gas, NGLs and condensate sales — 3,768 101 2,406 2,104 6,273 — 14,652 3,639 18,291 Other revenues — 2,670 1,034 49 945 1,646 — 6,344 (56 ) 6,288 Total $ 7,591 $ 22,123 $ 5,156 $ 3,041 $ 33,604 $ 19,347 $ 5,897 $ 96,759 $ 2,927 $ 99,686 Reportable Segments Six months ended June 30, 2019 Utica Shale Williston Basin DJ Basin Permian Basin Piceance Basin Barnett Shale Marcellus Shale Total reportable segments All other segments Total (In thousands) Major products / services lines Gathering services and related fees $ 15,086 $ 41,391 $ 7,745 $ 952 $ 62,395 $ 24,453 $ 12,094 $ 164,116 $ (2,045 ) $ 162,071 Natural gas, NGLs and condensate sales — 9,353 186 6,627 4,406 6,877 — 27,449 28,770 56,219 Other revenues — 5,578 2,041 81 2,083 3,302 — 13,085 (281 ) 12,804 Total $ 15,086 $ 56,322 $ 9,972 $ 7,660 $ 68,884 $ 34,632 $ 12,094 $ 204,650 $ 26,444 $ 231,094
Schedule of Information about Contract Assets from Contracts with Customers	The following table provides information about contract assets from contracts with customers: June 30, 2020 December 31, 2019 (In thousands) Contract assets, beginning of period $ 3,902 $ 8,755 Additions 15,074 18,077 Transfers out (1,876 ) (22,930 ) Contract assets, end of period $ 17,100 $ 3,902

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Schedule of assets by reportable segment	Assets by reportable segment follow. June 30, 2020 December 31, 2019 (In thousands) Assets (1): Utica Shale $ 210,592 $ 206,368 Ohio Gathering 269,504 275,000 Williston Basin 453,327 452,152 DJ Basin 203,866 205,308 Permian Basin 169,710 185,708 Piceance Basin 605,786 631,140 Barnett Shale 357,824 350,638 Marcellus Shale 183,896 184,631 Total reportable segment assets 2,454,505 2,490,945 Corporate and Other 131,997 83,153 Total assets $ 2,586,502 $ 2,574,098 (1) At June 30, 2020, Corporate and Other included $113.6 million relating to our investment in Double E (included in the Investment in equity method investees caption of the unaudited condensed consolidated balance sheet). At December 31, 2019, Corporate and Other included $34.7 million relating to our investment in Double E.
Schedule of segment reporting information	Revenues by reportable segment follow. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Revenues (1): Utica Shale $ 11,538 $ 7,591 $ 18,500 $ 15,086 Williston Basin 18,314 22,123 49,577 56,322 DJ Basin 6,292 5,156 14,251 9,972 Permian Basin 7,059 3,041 14,069 7,660 Piceance Basin 27,719 33,604 56,976 68,884 Barnett Shale 14,513 19,347 30,087 34,632 Marcellus Shale 5,928 5,897 12,163 12,094 Total reportable segments revenue 91,363 96,759 195,623 204,650 Corporate and Other 644 3,824 1,287 30,662 Eliminations — (897 ) — (4,218 ) Total revenues $ 92,007 $ 99,686 $ 196,910 $ 231,094 (1) Excludes revenues earned by Ohio Gathering due to equity method accounting. Depreciation and amortization, including the amortization expense associated with our favorable gas gathering contracts as reported in Other revenues, by reportable segment follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Depreciation and amortization (1): Utica Shale $ 1,920 $ 1,923 $ 3,847 $ 3,831 Williston Basin 6,487 4,734 12,982 10,170 DJ Basin 1,502 464 3,029 1,263 Permian Basin 1,387 1,163 2,732 2,235 Piceance Basin 11,306 11,810 22,604 23,601 Barnett Shale (2) 4,023 4,167 8,055 8,497 Marcellus Shale 2,300 2,286 4,600 4,569 Total reportable segment depreciation and amortization 28,925 26,547 57,849 54,166 Corporate and Other 941 653 1,917 1,187 Total depreciation and amortization $ 29,866 $ 27,200 $ 59,766 $ 55,353 (1) Excludes depreciation and amortization recognized by Ohio Gathering due to equity method accounting. (2) Includes the amortization expense associated with our favorable gas gathering contracts as reported in Other revenues . Cash paid for capital expenditures by reportable segment follow. Six months ended June 30, 2020 2019 (In thousands) Cash paid for capital expenditures (1): Utica Shale $ 1,482 $ 1,065 Williston Basin 7,423 14,230 DJ Basin 8,428 50,373 Permian Basin 4,921 28,163 Piceance Basin 404 1,497 Barnett Shale (2) 869 (37 ) Marcellus Shale 430 108 Total reportable segment capital expenditures 23,957 95,399 Corporate and Other 3,469 15,693 Total cash paid for capital expenditures $ 27,426 $ 111,092 (1) Excludes cash paid for capital expenditures by Ohio Gathering due to equity method accounting. (2) For the six months ended June 30, 2019, the amount includes sales tax reimbursements of $1.1 million.
Schedule of counterparties 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, 2020 2019 2020 2019 Percentage of total revenues (1): Counterparty A - Piceance Basin 11 % 12 % 11 % 11 % Counterparty B - Williston Basin * 11 % * 10 % Counterparty C - Barnett Shale * 14 % * 12 % (1) Excludes revenues earned by Ohio Gathering due to equity method accounting. * Less than 10%
Reconciliation of net income to adjusted EBITDA	Segment adjusted EBITDA by reportable segment follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Reportable segment adjusted EBITDA Utica Shale $ 10,693 $ 6,640 $ 16,621 $ 12,833 Ohio Gathering 7,514 9,939 15,453 19,149 Williston Basin 12,727 16,650 28,919 35,384 DJ Basin 4,339 2,816 10,250 5,489 Permian Basin 1,828 (656 ) 3,409 (1,206 ) Piceance Basin 21,734 24,584 45,291 50,583 Barnett Shale 8,510 11,208 17,270 22,582 Marcellus Shale 4,888 4,635 10,208 9,777 Total of reportable segments' measures of profit $ 72,233 $ 75,816 $ 147,421 $ 154,591 A reconciliation of income or loss before income taxes and income or loss from equity method investees to total of reportable segments' measures of profit or loss follows. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Reconciliation of income (loss) before income taxes and income (loss) from equity method investees to total of reportable segments' measures of profit: Income (loss) before income taxes and income (loss) from equity method investees $ 53,292 $ 4,256 $ 53,730 $ (35,326 ) Add: Corporate and Other expense 9,533 8,255 21,610 24,905 Interest expense 21,990 22,343 45,818 45,085 Gain on early extinguishment of debt (54,235 ) — (54,235 ) — Depreciation and amortization 29,866 27,200 59,766 55,353 Proportional adjusted EBITDA for equity method investees 7,514 9,939 15,453 19,149 Adjustments related to MVC shortfall payments 2,291 3,533 (3,151 ) (666 ) Adjustments related to capital reimbursement activity (237 ) (1,046 ) (448 ) (1,761 ) Unit-based and noncash compensation 1,846 1,553 4,569 4,079 Gain on asset sales, net (281 ) (287 ) (166 ) (1,248 ) Long-lived asset impairment 654 70 4,475 45,021 Total of reportable segments' measures of profit $ 72,233 $ 75,816 $ 147,421 $ 154,591
Schedule of Adjustments Related to Minimum Volume Commitments Shortfall Payments	Adjustments related to MVC shortfall payments by reportable segment follow. Three months ended June 30, 2020 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ 2,124 $ 167 $ — $ 2,291 Three months ended June 30, 2019 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ 2,081 $ — $ 1,452 $ 3,533 Six months ended June 30, 2020 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ (3,541 ) $ 390 $ — $ (3,151 ) Six months ended June 30, 2019 Williston Basin Piceance Basin Barnett Shale Total (In thousands) Adjustments related to expected MVC shortfall payments: $ (3,468 ) $ (103 ) $ 2,905 $ (666 )

PROPERTY, PLANT, AND EQUIPMEN_2

PROPERTY, PLANT, AND EQUIPMENT, NET (Tables)	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Schedule of property, plant, and equipment, net	Details on property, plant and equipment follow. June 30, 2020 December 31, 2019 (In thousands) Gathering and processing systems and related equipment $ 2,193,200 $ 2,182,950 Construction in progress 76,189 78,716 Land and line fill 10,440 10,137 Other 60,414 54,595 Total 2,340,243 2,326,398 Less accumulated depreciation 484,354 443,909 Property, plant and equipment, net $ 1,855,889 $ 1,882,489
Schedule of depreciation expense and capitalized interest costs	Depreciation expense and capitalized interest follow. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Depreciation expense $ 21,664 $ 18,866 $ 43,362 $ 38,686 Capitalized interest 328 2,446 819 4,361

AMORTIZING INTANGIBLE ASSETS (T

AMORTIZING INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible assets and liabilities subject to amortization	Details regarding our intangible assets, all of which are subject to amortization, follow: June 30, 2020 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (15,595 ) $ 8,600 Contract intangibles 278,448 (182,396 ) 96,052 Rights-of-way 157,202 (45,953 ) 111,249 Total intangible assets $ 459,845 $ (243,944 ) $ 215,901 December 31, 2019 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (15,125 ) $ 9,070 Contract intangibles 278,448 (169,549 ) 108,899 Rights-of-way 157,175 (42,866 ) 114,309 Total intangible assets $ 459,818 $ (227,540 ) $ 232,278
Recognized amortization expense in other revenues and cost and expenses	We recognized amortization expense in Other revenues as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Amortization expense – favorable gas gathering contracts $ (236 ) $ (363 ) $ (470 ) $ (752 ) We recognized amortization expense in costs and expenses as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Amortization expense – contract intangibles $ 6,423 $ 6,397 $ 12,847 $ 12,794 Amortization expense – rights-of-way 1,543 1,574 3,087 3,121
Estimated aggregate annual amortization expected to be recognized	The estimated aggregate annual amortization expected to be recognized for the remainder of 2020 and each of the four succeeding fiscal years follows. Intangible assets (In thousands) 2020 $ 15,951 2021 28,209 2022 25,142 2023 25,088 2024 14,917

EQUITY METHOD INVESTMENTS (Tabl

EQUITY METHOD INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Equity Method Investments And Joint Ventures [Abstract]
Equity Method Investments	As of June 30, 2020 and December 31, 2019, our ownership interest in Ohio Gathering was 38.3% and 38.5%, respectively, and provided below is a reconciliation of the difference at June 30, 2020 between the amount at which our ownership interest in Ohio Gathering is carried to the amount of our underlying investment per Ohio Gathering's books and records (in thousands). Investment in Ohio Gathering, June 30, 2020 $ 269,504 June cash distributions 2,403 Basis difference 220,922 Investment in Ohio Gathering (Books and records), May 31, 2020 $ 492,829 As noted in our 2019 Annual Report, in December 2019 an impairment loss of long-lived assets was recognized by OCC which brought our investment in OCC to zero. As a result, we have not recorded our portion of OCC’s net loss for the three and six months ended June 30, 2020 in the Income (loss) from equity method investees caption of our unaudited condensed consolidated statements of operations. Summarized statements of operations information for OGC and OCC follow (amounts represent 100% of investee financial information). Three months ended May 31, 2020 Three months ended May 31, 2019 OGC OCC OGC OCC (In thousands) Total revenues $ 27,334 $ 2,404 $ 35,262 $ 2,073 Total operating expenses 24,045 2,069 26,336 2,691 Net income (loss) 3,289 335 8,926 (619 ) Six months ended May 31, 2020 Six months ended May 31, 2019 OGC OCC OGC OCC (In thousands) Total revenues $ 57,402 $ 5,131 $ 68,728 $ 4,339 Total operating expenses 49,795 32,924 51,823 5,664 Net income (loss) 7,600 (27,793 ) 16,898 (1,326 )

DEFERRED REVENUE (Tables)

DEFERRED REVENUE (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
Rollforward of deferred revenue	A rollforward of current deferred revenue follows. Utica Shale Williston Basin DJ Basin Piceance Basin Barnett Shale Marcellus Shale Total current (In thousands) Current deferred revenue, January 1, 2020 $ 18 $ 1,933 $ 2,860 $ 7,014 $ 1,630 $ 38 $ 13,493 Additions 2 1,000 4,341 3,095 793 19 9,250 Less revenue recognized 9 967 2,483 3,092 819 19 7,389 Current deferred revenue, June 30, 2020 $ 11 $ 1,966 $ 4,718 $ 7,017 $ 1,604 $ 38 $ 15,354 A rollforward of noncurrent deferred revenue follows. Utica Shale Williston Basin DJ Basin Piceance Basin Barnett Shale Marcellus Shale Total noncurrent (In thousands) Noncurrent deferred revenue, January 1, 2020 $ 3 $ 3,634 $ 7,589 $ 17,710 $ 9,575 $ 198 $ 38,709 Additions 425 3,522 5,582 2,563 764 — 12,856 Less reclassification to current deferred revenue 2 967 4,341 3,095 793 19 9,217 Noncurrent deferred revenue, June 30, 2020 $ 426 $ 6,189 $ 8,830 $ 17,178 $ 9,546 $ 179 $ 42,348

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of debt and capital leases	Debt consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Summit Holdings' variable rate senior secured Revolving Credit Facility (2.93% at June 30, 2020 and 4.55% at December 31, 2019) due May 2022 $ 733,000 $ 677,000 Summit Holdings' 8.00% senior secured term loan due March 2021 35,000 — Summit Holdings' 5.5% senior unsecured notes due August 2022 274,224 300,000 Less unamortized debt issuance costs (1) (1,252 ) (1,686 ) Summit Holdings' 5.75% senior unsecured notes due April 2025 393,765 500,000 Less unamortized debt issuance costs (1) (3,583 ) (5,015 ) SMP Holdings' variable rate senior secured term loan (7.00% at June 30, 2020 and 7.80% at December 31, 2019) due May 2022 155,200 161,500 Less unamortized debt issuance costs (1) (3,222 ) (3,974 ) Total debt 1,583,133 1,627,825 Less current portion 38,000 5,546 Total long-term debt $ 1,545,133 $ 1,622,279 (1) Issuance costs are being amortized over the life of the term loan and the Senior Notes.

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Summary of the estimated fair value of debt instruments	A summary of the estimated fair value of our debt financial instruments follows. June 30, 2020 December 31, 2019 Carrying value Estimated fair value (Level 2) Carrying value Estimated fair value (Level 2) (In thousands) Summit Holdings 5.5% principal) $ 272,973 $ 180,531 $ 298,314 $ 266,750 Summit Holdings 5.75% principal) 390,183 211,977 494,985 382,708

PARTNERS' CAPITAL AND MEZZANI_2

PARTNERS' CAPITAL AND MEZZANINE CAPITAL (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Schedule of partner units activity	A rollforward of the number of common limited partner units follows. Common Units Units, December 31, 2019 (1) 45,318,866 Net units issued under the SMLP LTIP 308,364 Impact of GP Buy-In Transaction (2,084,174 ) Units, June 30, 2020 (1) 43,543,056 (1) As a result of the GP Buy-In Transaction, the recast of the historical financial statements resulted in a recasted common limited partner unit count of 45.3 million units at December 31, 2019. Prior to the GP Buy-In Transaction, the common limited partner unit count was 93.5 million units at December 31, 2019, and after adjusting these 93.5 million units for the effect of 1.2 million units issued through June 30, 2020 for the SMLP LTIP, and the GP Buy-In Transaction’s repurchase of 34.6 million units pledged under the Term Loan B, the 10.7 million units not pledged under the Term Loan B, and the 5.9 million units owned by ECP, the common limited partner unit count would have been an otherwise identical 43.5 million common limited partner units at June 30, 2020.
Details of cash distributions	Prior to the GP Buy-In Transaction, SMLP paid the following per-unit distributions during the three and six months ended June 30 (All payments represent per-unit distributions based on the SMLP common units outstanding prior to the GP Buy-In Transaction): Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 Per-unit distributions to unitholders $ — $ 0.2875 $ 0.125 $ 0.8625

EARNINGS PER UNIT (Tables)

EARNINGS PER UNIT (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of earnings per limited partner unit	The following table details the components of EPU. Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net income (loss) among limited partner interests: Net income (loss) attributable to limited partners $ 58,114 $ 4,369 $ 63,757 $ (10,341 ) Less net income attributable to Series A Preferred Units 7,125 7,125 14,250 14,250 Less net income attributable to Subsidiary Series A Preferred Units 1,397 — 2,342 — Net income (loss) attributable to common limited partners $ 49,592 $ (2,756 ) $ 47,165 $ (24,591 ) Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic (1) 44,650 45,319 44,985 45,319 Effect of nonvested phantom units 2,087 — 1,338 — Weighted-average common units outstanding – diluted 46,737 45,319 46,323 45,319 Income (Loss) per limited partner unit: Common unit – basic $ 1.11 $ (0.06 ) $ 1.05 $ (0.54 ) Common unit – diluted $ 1.06 $ (0.06 ) $ 1.02 $ (0.54 ) Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 4,139 — 3,014 17 (1) As a result of the GP Buy-In Transaction, our historical results are those of Summit Investments. The number of common units of 45.3 million represents those of Summit Investments and has been used for the earnings per unit calculations presented herein. As discussed in Note 9, the SMPH Term Loan is secured by 34.6 million SMLP common units owned by SMP Holdings. These common units are not included in the calculation of EPU because they are not deemed contingently issuable under GAAP.

LEASES, COMMITMENTS AND CONTI_2

LEASES, COMMITMENTS AND CONTINGENCIES (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of right-of-use assets and lease liabilities	Right-of-Use (“ROU”) assets (included in the Property, plant and equipment, net caption on our unaudited condensed consolidated balance sheet) and lease liabilities (included in the Other current liabilities and Other noncurrent liabilities captions on our unaudited condensed consolidated balance sheet) follow: June 30, 2020 December 31, 2019 (In thousands) ROU assets Operating $ 4,996 $ 3,580 Finance 2,253 3,159 $ 7,249 $ 6,739 Lease liabilities, current Operating $ 1,659 $ 1,221 Finance 826 1,246 $ 2,485 $ 2,467 Lease liabilities, noncurrent Operating $ 4,120 $ 2,513 Finance 310 676 $ 4,430 $ 3,189
Schedule of total rent expense related to operating leases	We recognize total lease expense incurred in general and administrative expenses. Lease expense related to operating leases, was as follows: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 (In thousands) Lease expense $ 937 $ 1,033 $ 1,890 $ 2,023
Schedule of accrued environmental remediation	A rollforward of the Partnership’s undiscounted accrued environmental remediation liabilities follows. Total (In thousands) Accrued environmental remediation, January 1, 2020 $ 4,651 Payments made (545 ) Accrued environmental remediation, June 30, 2020 $ 4,106

ORGANIZATION, BUSINESS OPERAT_2

ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Mar. 21, 2017	Feb. 25, 2016
Organization And Business Operations [Line Items]
Purchase agreement date	May 3, 2020
Common limited partner capital (shares)	43,543,056	45,318,866
Common Units | Energy Capital Partners
Organization And Business Operations [Line Items]
Common limited partner capital (shares)	5,915,827
Summit Midstream Partners Holdings L L C
Organization And Business Operations [Line Items]
SMLP common units pledged as collateral under the SMPH Term Loan			34,604,581
SMLP common units not pledged as collateral under the SMPH Term Loan				10,714,285
Common units retire	16,630,112
Summit Investments
Organization And Business Operations [Line Items]
Cash paid to Acquire investment	$ 35
Summit Investments | Common Units
Organization And Business Operations [Line Items]
Number of common units purchased.	10,000,000

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Restricted cash	$ 5,048	$ 27,392	$ 0
DFW Midstream
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Amount held in court's registry	5,400
Amount payable to customers	$ 1,900
Duration of amount payable to customer	4 months
Date of commencement of customers payment	Sep. 1, 2020
Double E
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Restricted cash		$ 27,400

REVENUE - Narrative1 (Details)

REVENUE - Narrative1 (Details)	Jun. 30, 2020
Maximum | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-07-01
Revenue From Contract With Customer [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	25 years

REVENUE - Schedule of Estimated

REVENUE - Schedule of Estimated Revenue Expected to be Recognized and MVC Shortfall Payments (Details) - Gathering Services and Related Fees $ in Thousands	Jun. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	6 months
Revenue, remaining performance obligation	$ 58,427
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	1 year
Revenue, remaining performance obligation	$ 102,127
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	1 year
Revenue, remaining performance obligation	$ 84,736
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	1 year
Revenue, remaining performance obligation	$ 66,693
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	1 year
Revenue, remaining performance obligation	$ 50,608
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period
Revenue, remaining performance obligation	$ 57,721

REVENUE - Schedule of Disaggreg

REVENUE - Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Total revenues	$ 92,007	$ 99,686	$ 196,910	$ 231,094
All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	644	2,927	1,287	26,444
Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	91,363	96,759	195,623	204,650
Reportable Segments | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	11,538	7,591	18,500	15,086
Reportable Segments | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	18,314	22,123	49,577	56,322
Reportable Segments | DJ Basin
Disaggregation Of Revenue [Line Items]
Total revenues	6,292	5,156	14,251	9,972
Reportable Segments | Permian Basin
Disaggregation Of Revenue [Line Items]
Total revenues	7,059	3,041	14,069	7,660
Reportable Segments | Piceance Basin
Disaggregation Of Revenue [Line Items]
Total revenues	27,719	33,604	56,976	68,884
Reportable Segments | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	14,513	19,347	30,087	34,632
Reportable Segments | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	5,928	5,897	12,163	12,094
Gathering Services and Related Fees
Disaggregation Of Revenue [Line Items]
Total revenues	73,911	75,107	157,703	162,071
Gathering Services and Related Fees | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	0	(656)	0	(2,045)
Gathering Services and Related Fees | Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	73,911	75,763	157,703	164,116
Gathering Services and Related Fees | Reportable Segments | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	11,538	7,591	18,500	15,086
Gathering Services and Related Fees | Reportable Segments | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	12,407	15,685	36,204	41,391
Gathering Services and Related Fees | Reportable Segments | DJ Basin
Disaggregation Of Revenue [Line Items]
Total revenues	5,228	4,021	12,083	7,745
Gathering Services and Related Fees | Reportable Segments | Permian Basin
Disaggregation Of Revenue [Line Items]
Total revenues	2,711	586	5,022	952
Gathering Services and Related Fees | Reportable Segments | Piceance Basin
Disaggregation Of Revenue [Line Items]
Total revenues	26,222	30,555	53,411	62,395
Gathering Services and Related Fees | Reportable Segments | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	9,877	11,428	20,320	24,453
Gathering Services and Related Fees | Reportable Segments | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	5,928	5,897	12,163	12,094
Natural Gas, NGLs and Condensate Sales
Disaggregation Of Revenue [Line Items]
Total revenues	10,683	18,291	24,463	56,219
Natural Gas, NGLs and Condensate Sales | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	0	3,639	0	28,770
Natural Gas, NGLs and Condensate Sales | Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	10,683	14,652	24,463	27,449
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0	0	0	0
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	3,131	3,768	7,455	9,353
Natural Gas, NGLs and Condensate Sales | Reportable Segments | DJ Basin
Disaggregation Of Revenue [Line Items]
Total revenues	71	101	141	186
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Permian Basin
Disaggregation Of Revenue [Line Items]
Total revenues	4,222	2,406	8,734	6,627
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Piceance Basin
Disaggregation Of Revenue [Line Items]
Total revenues	401	2,104	1,404	4,406
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	2,858	6,273	6,729	6,877
Natural Gas, NGLs and Condensate Sales | Reportable Segments | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0	0	0	0
Other Revenues
Disaggregation Of Revenue [Line Items]
Total revenues	7,413	6,288	14,744	12,804
Other Revenues | All Other Segments
Disaggregation Of Revenue [Line Items]
Total revenues	644	(56)	1,287	(281)
Other Revenues | Reportable Segments
Disaggregation Of Revenue [Line Items]
Total revenues	6,769	6,344	13,457	13,085
Other Revenues | Reportable Segments | Utica Shale
Disaggregation Of Revenue [Line Items]
Total revenues	0	0	0	0
Other Revenues | Reportable Segments | Williston Basin
Disaggregation Of Revenue [Line Items]
Total revenues	2,776	2,670	5,918	5,578
Other Revenues | Reportable Segments | DJ Basin
Disaggregation Of Revenue [Line Items]
Total revenues	993	1,034	2,027	2,041
Other Revenues | Reportable Segments | Permian Basin
Disaggregation Of Revenue [Line Items]
Total revenues	126	49	313	81
Other Revenues | Reportable Segments | Piceance Basin
Disaggregation Of Revenue [Line Items]
Total revenues	1,096	945	2,161	2,083
Other Revenues | Reportable Segments | Barnett Shale
Disaggregation Of Revenue [Line Items]
Total revenues	1,778	1,646	3,038	3,302
Other Revenues | Reportable Segments | Marcellus Shale
Disaggregation Of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0

REVENUE - Schedule of Informati

REVENUE - Schedule of Information about Contract Assets from Contracts with Customers (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Contract With Customer Asset And Liability [Abstract]
Contract assets, beginning of period	$ 3,902	$ 8,755
Additions	15,074	18,077
Transfers out	(1,876)	(22,930)
Contract assets, end of period	$ 17,100	$ 3,902

REVENUE - Narrative (Details)

REVENUE - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Revenue From Contract With Customer [Line Items]
Receivables with customers		$ 56,500		$ 56,500	$ 90,400
Contract assets included in accounts receivable	$ 17,100	17,100	$ 17,100	17,100	$ 3,902	$ 8,755
Gathering Services and Related Fees
Revenue From Contract With Customer [Line Items]
Contract liabilities, revenue	$ 2,300	$ 2,700	$ 4,700	$ 5,400

SEGMENT INFORMATION - Assets, R

SEGMENT INFORMATION - Assets, Revenues, Depreciation and Amortization, and Capital Expenditures by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Assets	$ 2,586,502		$ 2,586,502		$ 2,574,098
Revenues	92,007	$ 99,686	196,910	$ 231,094
Depreciation and amortization	29,866	27,200	59,766	55,353
Capital expenditures			27,426	111,092
Reportable Segments
Segment Reporting Information [Line Items]
Assets	2,454,505		2,454,505		2,490,945
Revenues	91,363	96,759	195,623	204,650
Depreciation and amortization	28,925	26,547	57,849	54,166
Capital expenditures			23,957	95,399
Reportable Segments | Utica Shale
Segment Reporting Information [Line Items]
Assets	210,592		210,592		206,368
Revenues	11,538	7,591	18,500	15,086
Depreciation and amortization	1,920	1,923	3,847	3,831
Capital expenditures			1,482	1,065
Reportable Segments | Ohio Gathering
Segment Reporting Information [Line Items]
Assets	269,504		269,504		275,000
Reportable Segments | Williston Basin
Segment Reporting Information [Line Items]
Assets	453,327		453,327		452,152
Revenues	18,314	22,123	49,577	56,322
Depreciation and amortization	6,487	4,734	12,982	10,170
Capital expenditures			7,423	14,230
Reportable Segments | DJ Basin
Segment Reporting Information [Line Items]
Assets	203,866		203,866		205,308
Revenues	6,292	5,156	14,251	9,972
Depreciation and amortization	1,502	464	3,029	1,263
Capital expenditures			8,428	50,373
Reportable Segments | Barnett Shale
Segment Reporting Information [Line Items]
Assets	357,824		357,824		350,638
Revenues	14,513	19,347	30,087	34,632
Depreciation and amortization	4,023	4,167	8,055	8,497
Capital expenditures			869	(37)
Reportable Segments | Permian Basin
Segment Reporting Information [Line Items]
Assets	169,710		169,710		185,708
Revenues	7,059	3,041	14,069	7,660
Depreciation and amortization	1,387	1,163	2,732	2,235
Capital expenditures			4,921	28,163
Reportable Segments | Marcellus Shale
Segment Reporting Information [Line Items]
Assets	183,896		183,896		184,631
Revenues	5,928	5,897	12,163	12,094
Depreciation and amortization	2,300	2,286	4,600	4,569
Capital expenditures			430	108
Reportable Segments | Piceance Basin
Segment Reporting Information [Line Items]
Assets	605,786		605,786		631,140
Revenues	27,719	33,604	56,976	68,884
Depreciation and amortization	11,306	11,810	22,604	23,601
Capital expenditures			404	1,497
Corporate and Other
Segment Reporting Information [Line Items]
Assets	131,997		131,997		$ 83,153
Revenues	644	3,824	1,287	30,662
Depreciation and amortization	$ 941	653	1,917	1,187
Capital expenditures			$ 3,469	15,693
Eliminations
Segment Reporting Information [Line Items]
Revenues		$ (897)		$ (4,218)

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Equity method investment	$ 383,058		$ 309,728
Capital expenditures	27,426	$ 111,092
Corporate
Segment Reporting Information [Line Items]
Capital expenditures		300
Corporate and Other
Segment Reporting Information [Line Items]
Capital expenditures	3,469	15,693
Corporate and Other | Double E
Segment Reporting Information [Line Items]
Capital expenditures			$ 34,700
Equity method investment	113,600
Reportable Segments
Segment Reporting Information [Line Items]
Capital expenditures	23,957	95,399
Reportable Segments | Barnett Shale
Segment Reporting Information [Line Items]
Sales tax reimbursement		1,100
Capital expenditures	$ 869	$ (37)

SEGMENT INFORMATION - Concentra

SEGMENT INFORMATION - Concentration Risk (Details) - Sales Revenue, Net - Customer Concentration Risk	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Counterparty A - Piceance Basin
Segment Reporting Information [Line Items]
Concentration risk, percentage	11.00%	12.00%	11.00%	11.00%
Counterparty B - Williston Basin
Segment Reporting Information [Line Items]
Concentration risk, percentage		11.00%		10.00%
Counterparty C - Barnett Shale
Segment Reporting Information [Line Items]
Concentration risk, percentage		14.00%		12.00%

SEGMENT INFORMATION - Adjusted

SEGMENT INFORMATION - Adjusted EBITDA by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 72,233	$ 75,816	$ 147,421	$ 154,591
Utica Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	10,693	6,640	16,621	12,833
Ohio Gathering
Segment Reporting Information [Line Items]
Adjusted EBITDA	7,514	9,939	15,453	19,149
Williston Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	12,727	16,650	28,919	35,384
DJ Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	4,339	2,816	10,250	5,489
Permian Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	1,828	(656)	3,409	(1,206)
Piceance Basin
Segment Reporting Information [Line Items]
Adjusted EBITDA	21,734	24,584	45,291	50,583
Barnett Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	8,510	11,208	17,270	22,582
Marcellus Shale
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 4,888	$ 4,635	$ 10,208	$ 9,777

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Net Income (Loss) to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting [Abstract]
Income (loss) before income taxes and income (loss) from equity method investees	$ 53,292	$ 4,256	$ 53,730	$ (35,326)
Add:
Corporate and Other expense	9,533	8,255	21,610	24,905
Interest expense	21,990	22,343	45,818	45,085
Gain on early extinguishment of debt	(54,235)		(54,235)	0
Depreciation and amortization	29,866	27,200	59,766	55,353
Proportional adjusted EBITDA for equity method investees	7,514	9,939	15,453	19,149
Adjustments related to MVC shortfall payments	2,291	3,533	(3,151)	(666)
Adjustments related to capital reimbursement activity	(237)	(1,046)	(448)	(1,761)
Unit-based and noncash compensation	1,846	1,553	4,569	4,079
Gain on asset sales, net	(281)	(287)	(166)	(1,248)
Long-lived asset impairment	654	70	4,475	45,021
Total of reportable segments' measures of profit	$ 72,233	$ 75,816	$ 147,421	$ 154,591

SEGMENT INFORMATION - Schedule

SEGMENT INFORMATION - Schedule of Adjustments Related to Minimum Volume Commitments Shortfall Payments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Adjustments related to MVC shortfall payments	$ 2,291	$ 3,533	$ (3,151)	$ (666)
Williston Basin
Segment Reporting Information [Line Items]
Adjustments related to MVC shortfall payments	2,124	2,081	(3,541)	(3,468)
Piceance Basin
Segment Reporting Information [Line Items]
Adjustments related to MVC shortfall payments	$ 167		$ 390	(103)
Barnett Shale
Segment Reporting Information [Line Items]
Adjustments related to MVC shortfall payments		$ 1,452		$ 2,905

PROPERTY, PLANT, AND EQUIPMEN_3

PROPERTY, PLANT, AND EQUIPMENT, NET - Schedule of Property, Plant, and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,340,243	$ 2,326,398
Less accumulated depreciation	484,354	443,909
Property, plant and equipment, net	1,855,889	1,882,489
Gathering and processing systems and related equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,193,200	2,182,950
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	76,189	78,716
Land and line fill
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,440	10,137
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 60,414	$ 54,595

PROPERTY, PLANT, AND EQUIPMEN_4

PROPERTY, PLANT, AND EQUIPMENT, NET - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Line Items]
Asset impairment charges			$ 10.2
Rights-of-way
Property, Plant and Equipment [Line Items]
Asset impairment charges			0.5
DJ Basin
Property, Plant and Equipment [Line Items]
Asset impairment charges	$ 34.7	$ 3.6
Barnett Shale | Fixed Assets
Property, Plant and Equipment [Line Items]
Asset impairment charges			$ 9.7

PROPERTY, PLANT, AND EQUIPMEN_5

PROPERTY, PLANT, AND EQUIPMENT, NET - Schedule of Depreciation Expense and Capitalized Interest (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 21,664	$ 18,866	$ 43,362	$ 38,686
Capitalized interest	$ 328	$ 2,446	$ 819	$ 4,361

AMORTIZING INTANGIBLE ASSETS -

AMORTIZING INTANGIBLE ASSETS - Intangible Assets and Liabilities Subject to Amortization (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 459,845	$ 459,818
Accumulated amortization	(243,944)	(227,540)
Net	215,901	232,278
Favorable gas gathering contracts
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	24,195	24,195
Accumulated amortization	(15,595)	(15,125)
Net	8,600	9,070
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	278,448	278,448
Accumulated amortization	(182,396)	(169,549)
Net	96,052	108,899
Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	157,202	157,175
Accumulated amortization	(45,953)	(42,866)
Net	$ 111,249	$ 114,309

AMORTIZING INTANGIBLE ASSETS _2

AMORTIZING INTANGIBLE ASSETS - Recognized Amortization Expense in Other Revenues and Cost and Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Revenue | Favorable gas gathering contracts
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ (236)	$ (363)	$ (470)	$ (752)
Costs And Expenses | Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization expense	6,423	6,397	12,847	12,794
Costs And Expenses | Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 1,543	$ 1,574	$ 3,087	$ 3,121

AMORTIZING INTANGIBLE ASSETS _3

AMORTIZING INTANGIBLE ASSETS - Estimated Aggregate Annual Amortization Expected to be Recognized (Details) $ in Thousands	Jun. 30, 2020USD ($)
Intangible assets
2020	$ 15,951
2021	28,209
2022	25,142
2023	25,088
2024	$ 14,917

EQUITY METHOD INVESTMENTS - Nar

EQUITY METHOD INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jun. 26, 2019
Schedule Of Equity Method Investments [Line Items]
Asset contribution to an equity method investment			$ 0	$ 23,643
Cash distribution to partnership			0	7,252
Additional cash investments			79,700		$ 18,300
Investment in equity method investees	$ 383,058		383,058		$ 309,728
Income (loss) from equity method investees	3,040	$ (79)	6,351	$ (520)
Principal Owner
Schedule Of Equity Method Investments [Line Items]
Cash distribution to partnership			7,300
Double E
Schedule Of Equity Method Investments [Line Items]
Parental maximum guaranty for capital calls not met by summit permian transmission						$ 350,000
Remaining capital contributions	229,000		229,000
Net assets	113,600		113,600
Result of operations	$ 0		0
Double E | Principal Owner
Schedule Of Equity Method Investments [Line Items]
Asset contribution to an equity method investment			$ 23,600
Percentage of ownership interest	70.00%		70.00%
Double E | JV Partner
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest	30.00%		30.00%
Cash contribution			$ 7,300
OGC | Principal Owner
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest	38.30%		38.30%		38.50%
OCC
Schedule Of Equity Method Investments [Line Items]
Investment in equity method investees	$ 0		$ 0
Income (loss) from equity method investees	$ 0		$ 0

EQUITY METHOD INVESTMENTS - Rol

EQUITY METHOD INVESTMENTS - Rollforward of the Investment in Equity Method Investees (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Schedule Of Equity Method Investments [Line Items]
Investment in Ohio Gathering, June 30, 2020	$ 383,058	$ 383,058
June cash distributions		12,749	$ 18,217
Investment in Ohio Gathering (Books and records), May 31, 2020		309,728
OGC | Summit Midstream Partners, LLC
Schedule Of Equity Method Investments [Line Items]
Investment in Ohio Gathering, June 30, 2020	269,504	$ 269,504
June cash distributions	2,403
Basis difference	220,922
Investment in Ohio Gathering (Books and records), May 31, 2020	$ 492,829

EQUITY METHOD INVESTMENTS - Sta

EQUITY METHOD INVESTMENTS - Statements of Operations Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
OGC
Schedule Of Equity Method Investments [Line Items]
Total revenues	$ 27,334	$ 35,262	$ 57,402	$ 68,728
Total operating expenses	24,045	26,336	49,795	51,823
Net income (loss)	3,289	8,926	7,600	16,898
OCC
Schedule Of Equity Method Investments [Line Items]
Total revenues	2,404	2,073	5,131	4,339
Total operating expenses	2,069	2,691	32,924	5,664
Net income (loss)	$ 335	$ (619)	$ (27,793)	$ (1,326)

DEFERRED REVENUE - Rollforward

DEFERRED REVENUE - Rollforward of deferred revenue (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	$ 13,493
Current deferred revenue, Additions	9,250
Current deferred revenue, Less revenue recognized	7,389
Current deferred revenue, ending balance	15,354
Noncurrent deferred revenue, beginning balance	38,709
Noncurrent deferred revenue, Additions	12,856
Noncurrent deferred revenue, Less reclassification to current deferred revenue	9,217
Noncurrent deferred revenue, ending balance	42,348
Utica Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	18
Current deferred revenue, Additions	2
Current deferred revenue, Less revenue recognized	9
Current deferred revenue, ending balance	11
Noncurrent deferred revenue, beginning balance	3
Noncurrent deferred revenue, Additions	425
Noncurrent deferred revenue, Less reclassification to current deferred revenue	2
Noncurrent deferred revenue, ending balance	426
Williston Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,933
Current deferred revenue, Additions	1,000
Current deferred revenue, Less revenue recognized	967
Current deferred revenue, ending balance	1,966
Noncurrent deferred revenue, beginning balance	3,634
Noncurrent deferred revenue, Additions	3,522
Noncurrent deferred revenue, Less reclassification to current deferred revenue	967
Noncurrent deferred revenue, ending balance	6,189
DJ Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	2,860
Current deferred revenue, Additions	4,341
Current deferred revenue, Less revenue recognized	2,483
Current deferred revenue, ending balance	4,718
Noncurrent deferred revenue, beginning balance	7,589
Noncurrent deferred revenue, Additions	5,582
Noncurrent deferred revenue, Less reclassification to current deferred revenue	4,341
Noncurrent deferred revenue, ending balance	8,830
Piceance Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	7,014
Current deferred revenue, Additions	3,095
Current deferred revenue, Less revenue recognized	3,092
Current deferred revenue, ending balance	7,017
Noncurrent deferred revenue, beginning balance	17,710
Noncurrent deferred revenue, Additions	2,563
Noncurrent deferred revenue, Less reclassification to current deferred revenue	3,095
Noncurrent deferred revenue, ending balance	17,178
Barnett Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,630
Current deferred revenue, Additions	793
Current deferred revenue, Less revenue recognized	819
Current deferred revenue, ending balance	1,604
Noncurrent deferred revenue, beginning balance	9,575
Noncurrent deferred revenue, Additions	764
Noncurrent deferred revenue, Less reclassification to current deferred revenue	793
Noncurrent deferred revenue, ending balance	9,546
Marcellus Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	38
Current deferred revenue, Additions	19
Current deferred revenue, Less revenue recognized	19
Current deferred revenue, ending balance	38
Noncurrent deferred revenue, beginning balance	198
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	19
Noncurrent deferred revenue, ending balance	$ 179

DEBT - Components of Long-Term

DEBT - Components of Long-Term Debt (Details) - USD ($) $ in Thousands		Jun. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Long-term debt		$ 1,545,133	$ 1,622,279
Summit Midstream Partners Holdings L L C
Line of Credit Facility [Line Items]
Total debt		1,583,133	1,627,825
Less current portion		38,000	5,546
Long-term debt		1,545,133	1,622,279
Summit Midstream Partners Holdings L L C | Senior Secured Revolving Credit Facility Due May 2022
Line of Credit Facility [Line Items]
Revolving credit facility		733,000	677,000
Summit Midstream Partners Holdings L L C | Senior Secured Term Loan Due May 2022
Line of Credit Facility [Line Items]
Revolving credit facility		155,200	161,500
Less unamortized debt issuance costs	[1]	(3,222)	(3,974)
Summit Midstream Partners Holdings L L C | Senior Notes Due August 2022
Line of Credit Facility [Line Items]
Unsecured notes		274,224	300,000
Less unamortized debt issuance costs	[1]	(1,252)	(1,686)
Summit Midstream Partners Holdings L L C | Senior Notes Due April 2025
Line of Credit Facility [Line Items]
Unsecured notes		393,765	500,000
Less unamortized debt issuance costs	[1]	(3,583)	(5,015)
Summit Midstream Partners Holdings L L C | Senior Secured Term Loan Due March 2021
Line of Credit Facility [Line Items]
Revolving credit facility		$ 35,000	$ 0
[1]	Issuance costs are being amortized over the life of the term loan and the Senior Notes.

DEBT - Components of Long-Ter_2

DEBT - Components of Long-Term Debt (Parenthetical) (Details) - Summit Midstream Partners Holdings L L C	Jun. 30, 2020	Dec. 31, 2019
Senior Secured Term Loan Due May 2022
Line of Credit Facility [Line Items]
Variable interest rate	7.00%	7.80%
Senior Secured Revolving Credit Facility Due May 2022
Line of Credit Facility [Line Items]
Variable interest rate	2.93%	4.55%
Senior Notes Due August 2022
Line of Credit Facility [Line Items]
Stated interest rate	5.50%	5.50%
Senior Notes Due April 2025
Line of Credit Facility [Line Items]
Stated interest rate	5.75%	5.75%
Senior Secured Term Loan Due March 2021
Line of Credit Facility [Line Items]
Stated interest rate	8.00%	8.00%

DEBT - Revolving Credit Facilit

DEBT - Revolving Credit Facility (Narrative) (Details) - Revolving credit facility	6 Months Ended
	Jun. 30, 2020USD ($)
Line of Credit Facility [Line Items]
Borrowing capacity	$ 1,250,000,000
Revolving credit facility maturity date	2022-05
Accordion feature	$ 250,000,000
Commitment fee on unused portion of the facility	0.50%
Interest rate at period end	2.93%
Unused portion under the facility	$ 512,900,000
Line of credit facility, outstanding amount	4,100,000
Current borrowing capacity	191,000,000
Debt issuance costs	5,400,000
Debt defaults	$ 0
LIBOR
Line of Credit Facility [Line Items]
Applicable margin	2.75%
Minimum
Line of Credit Facility [Line Items]
Commitment fee on unused portion of the facility	0.30%
Minimum | ABR
Line of Credit Facility [Line Items]
Applicable margin	0.75%
Minimum | LIBOR
Line of Credit Facility [Line Items]
Applicable margin	1.75%
Maximum
Line of Credit Facility [Line Items]
Commitment fee on unused portion of the facility	0.50%
Maximum | ABR
Line of Credit Facility [Line Items]
Applicable margin	1.75%
Maximum | LIBOR
Line of Credit Facility [Line Items]
Applicable margin	2.75%

DEBT - Summit Holdings Term Loa

DEBT - Summit Holdings Term Loans (Narrative) (Details) $ in Millions	May 28, 2020USD ($)	Jun. 30, 2020USD ($)
Debt Instrument [Line Items]
Line of credit facility description	(i) a Term Loan Credit Agreement (the “ECP NewCo Term Loan Credit Agreement”), with SMP TopCo, LLC, a Delaware limited liability company and affiliate of ECP (“ECP NewCo”), as lender and administrative agent, and Mizuho Bank (USA), as collateral agent (“Mizuho”), in a principal amount of $28.2 million (the “ECP NewCo Loan”), and (ii) a Term Loan Credit Agreement (the “ECP Holdings Term Loan Credit Agreement” and together with the ECP NewCo Term Loan Credit Agreement, the “ECP Term Loan Credit Agreements”), with ECP Holdings, as lender, and ECP NewCo, as administrative agent and Mizuho, as collateral agent, in a principal amount of $6.8 million (the “ECP Holdings Loan” and together with the ECP NewCo Loan, the “ECP Loans”). The ECP Loans mature on March 31, 2021 and are included in the current portion of long-term debt. The ECP Loans under each ECP Term Loan Credit Agreement bear interest at a rate of 8.00% per annum, with the interest expense due at maturity of the ECP Loans.
ECP NewCo Term Loan Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	$ 28.2
ECP Term Loan Credit Agreements [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	$ 6.8
Maturity date	Mar. 31, 2021
Stated interest rate	8.00%
Cumulative payment obligations, maximum		$ 50
ECP Term Loan Credit Agreements [Member] | Minimum [Member]
Debt Instrument [Line Items]
Ratio of consolidated trailing 12-month EBITDA to net interest expense		0.0250
ECP Term Loan Credit Agreements [Member] | Maximum
Debt Instrument [Line Items]
Ratio of total net indebtedness to consolidated trailing 12-month EBITDA		0.0550
Ratio of first lien net indebtedness to consolidated trailing 12-month EBITDA		0.0375

DEBT - Senior Notes (Narrative)

DEBT - Senior Notes (Narrative) (Details) - USD ($)	1 Months Ended
	Nov. 30, 2018	Feb. 28, 2017	Jul. 31, 2014	Jun. 30, 2020
Guarantor Subsidiaries
Debt Instrument [Line Items]
Cumulative percentage ownership in subsidiary	100.00%
5.75% Senior Notes
Debt Instrument [Line Items]
Stated interest rate		5.75%	5.75%
Maturity date		Apr. 15, 2025
Debt face amount		$ 500,000,000
Summit Holdings and Finance Corporation | Senior Notes Due August 2022
Debt Instrument [Line Items]
Senior unsecured notes			$ 300,000,000
Stated interest rate			5.50%	5.50%
Maturity date			Aug. 15, 2022
Finance Corp | Summit Holdings
Debt Instrument [Line Items]
Cumulative percentage ownership in subsidiary			100.00%

DEBT - SMP Holdings Term Loan (

DEBT - SMP Holdings Term Loan (Narrative) (Details) - USD ($)	Apr. 17, 2020	Mar. 21, 2017	Jun. 30, 2020	Jun. 30, 2020
Summit Midstream Partners Holdings L L C
Debt Instrument [Line Items]
SMLP common units pledged as collateral under the SMPH Term Loan		34,604,581
Term Loan B [Member]
Debt Instrument [Line Items]
Debt defaults		$ 300,000
Maturity date		May 15, 2022
Minimum interest coverage ratio				2.00%
Frequency of periodic payment of principal amounts				quarterly
Percentage of original principal amounts as repayment				1.00%
Derivative, notional amount	$ 125,000,000
Derivative, beginning date	Apr. 30, 2020
Derivative, maturity date	Apr. 30, 2022
Unsettled gain			$ 100,000	$ 100,000
Debt issuance costs incurred				$ 200,000
Term Loan B [Member] | Summit Midstream Partners Holdings L L C
Debt Instrument [Line Items]
Securities owned and pledged as collateral, description				(i) a perfected first-priority lien on, and pledge of, (A) all of the capital stock issued by SMP Holdings, (B) 34.6 million SMLP common units owned by SMP Holdings, (C) all of the equity interests owned by SMP Holdings in the General Partner, and (ii) substantially all other personal property of SMP Holdings.
SMLP common units pledged as collateral under the SMPH Term Loan			34,600,000	34,600,000
ABR | Term Loan B [Member]
Debt Instrument [Line Items]
Applicable margin		5.00%
LIBOR | Term Loan B [Member]
Debt Instrument [Line Items]
Applicable margin		6.00%
Derivative, fixed interest rate	1.00%

DEBT - Repurchases (Narrative)

DEBT - Repurchases (Narrative) (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jul. 31, 2014
Debt Instrument [Line Items]
Gain on early extinguishment of debt	$ 54,235,000	$ 54,235,000	$ 0
Summit Holdings and Finance Corporation | Senior Notes Due August 2022
Debt Instrument [Line Items]
Senior Notes repurchased	25,800,000	25,800,000
Senior unsecured notes	$ 300,000,000	$ 300,000,000
Stated interest rate	5.50%	5.50%		5.50%
Gain on early extinguishment of debt	$ 9,200,000	$ 9,200,000
Write-off of debt issuance costs	100,000	100,000
Summit Holdings and Finance Corporation | Senior Notes Due April 2025
Debt Instrument [Line Items]
Senior Notes repurchased	106,200,000	106,200,000
Senior unsecured notes	$ 500,000,000	$ 500,000,000
Stated interest rate	5.75%	5.75%
Gain on early extinguishment of debt	$ 45,100,000	$ 45,100,000
Write-off of debt issuance costs	$ 1,000,000	$ 1,000,000

FINANCIAL INSTRUMENTS - Concent

FINANCIAL INSTRUMENTS - Concentration Risk - Narrative (Details) - Customer	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
CONCENTRATIONS OF RISK
Number of top customers	5
Five Largest Customers | Accounts Receivable | Customer Concentration Risk
CONCENTRATIONS OF RISK
Concentration risk, percentage	50.00%	46.00%

FINANCIAL INSTRUMENTS - Fair va

FINANCIAL INSTRUMENTS - Fair value of Debt Instruments (Details) - Summit Holdings - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
5.5% Senior Notes | Carrying value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	$ 272,973	$ 298,314
5.5% Senior Notes | Fair Value | Estimated fair value (Level 2)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	180,531	266,750
5.75% Senior Notes | Carrying value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	390,183	494,985
5.75% Senior Notes | Fair Value | Estimated fair value (Level 2)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	$ 211,977	$ 382,708

FINANCIAL INSTRUMENTS - Fair _2

FINANCIAL INSTRUMENTS - Fair value of Debt Instruments (Parenthetical) (Details) - Summit Holdings - USD ($)	Jun. 30, 2020	Dec. 31, 2019
5.5% Senior Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	5.50%	5.50%
Debt face amount	$ 300,000,000	$ 300,000,000
5.75% Senior Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate	5.75%	5.75%
Debt face amount	$ 500,000,000	$ 500,000,000

PARTNERS' CAPITAL AND MEZZANI_3

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Partners' Capital and Schedule of Units (Details) - Common Units	6 Months Ended
	Jun. 30, 2020shares
Rollforwards of the number of partner units
Units, beginning balance (in shares)	45,318,866
Net units issued under the SMLP LTIP (in shares)	308,364
Impact of GP Buy-In Transaction	(2,084,174)
Units, ending balance (in shares)	43,543,056

PARTNERS' CAPITAL AND MEZZANI_4

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Partners' Capital and Schedule of Units (Parenthetical) (Details) - shares	Jun. 30, 2020	Dec. 31, 2019
Partners Capital [Line Items]
Common limited partner capital (in shares), issued	43,543,056	45,318,866
Common Units
Partners Capital [Line Items]
Partners capital account units	43.5	45.3
Common limited partner capital (in shares), issued	1.2
Common Units | Term Loan B [Member]
Partners Capital [Line Items]
Common units pledged as collateral	34.6
Common units not pledged as collateral	10.7
Common Units | Energy Capital Partners
Partners Capital [Line Items]
Common units owned by ECP	5.9
Previously Reported | Common Units
Partners Capital [Line Items]
Partners capital account units		93.5

PARTNERS' CAPITAL AND MEZZANI_5

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	May 28, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Partners Capital [Line Items]
Preferred units issued			300,000	300,000		300,000
Series A Preferred Units
Partners Capital [Line Items]
Preferred units issued			50,000	50,000		30,000	300,000
Interest in partnership per unit			$ 1,000	$ 1,000		$ 1,000	$ 1,000
Series A Preferred Units | Paid-in-Kind Distributions
Partners Capital [Line Items]
Pro-rated issuance of preferred units			490	1,397
Pro-rated distribution of preferred units			$ 30.7320	$ 17.2579
Pro-rated distribution of preferred units					$ 70
Pro-rated issuance of preferred units related to undrawn commitment				38
Series A Preferred Units | Double E
Partners Capital [Line Items]
Proceeds from issuance of common limited partners units				$ 48,700
Common Units | Summit Midstream Partners, LP
Partners Capital [Line Items]
General partner units converted		8,750,000
Common Units | Energy Capital Partners
Partners Capital [Line Items]
Number of common units purchased.	8,059,609
Exercise price of Warrants	$ 1.023
Valuation of warrants	$ 2,300		$ 2,300	2,300
Warrant or right, reason for issuance, description	The ECP Warrants also provide that the Partnership will file a registration statement to register the common units issuable upon exercise of the ECP Warrants no later than 90 days following the Closing Date and use commercially reasonable efforts to cause such registration statement to become effective. Upon exercise of the ECP Warrants, each of ECP NewCo and ECP Holdings may receive, at its election: (i) a number of common units equal to the number of common units for which the ECP Warrant is being exercised, if exercising the ECP Warrant by cash payment of the exercise price; (ii) a number of common units equal to the product of the number of common units being exercised multiplied by (a) the difference between the average of the daily volume-weighted average price (“VWAP”) of the common units on the New York Stock Exchange (the “NYSE”) on each of the three trading days prior to the delivery of the notice of exercise (the “VWAP Average”) and the exercise price (the “VWAP Difference”), divided by (b) the VWAP Average; and/or (iii) an amount in cash, to the extent that the Partnership’s leverage ratio would be at least 0.5x less than the maximum applicable ratio set forth in the Revolving Credit Facility, equal to the product of (a) the number of common units exercised and (b) the VWAP Difference, subject to certain adjustments under the ECP Warrants.
Common Units | Energy Capital Partners | ECP Holdings Warrant
Partners Capital [Line Items]
Number of common units purchased.	1,940,391
Common Units | Maximum | Energy Capital Partners
Partners Capital [Line Items]
Exercise price of Warrants	$ 2
Common units, issued	10,000,000
General Partner | Summit Midstream Partners, LP
Partners Capital [Line Items]
General partner interest		2.00%
General Partner | Common Units
Partners Capital [Line Items]
Cash paid to Acquire investment				$ 35,000
Number of common units purchased.				10,000,000
Advisory fees and other direct costs				$ 6,800
Fair value of warrants				$ 2,300

PARTNERS' CAPITAL AND MEZZANI_6

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Cash Distributions Paid and Declared (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Per-unit annual distributions to unitholders (in dollars per unit)	$ 0.2875	$ 0.125	$ 0.8625

EARNINGS PER UNIT (Details)

EARNINGS PER UNIT (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners		$ 58,114	$ 4,369	$ 63,757	$ (10,341)
Phantom Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU		4,139		3,014	17
Limited Partner Interest Before Subordinated Units Converted To Common Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners		$ 58,114	4,369	$ 63,757	$ (10,341)
Series A Preferred Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners		7,125	7,125	14,250	14,250
Series A Preferred Units | Subsidiaries
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners		1,397		2,342
Common units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners		$ 49,592	$ (2,756)	$ 47,165	$ (24,591)
Basic (shares)	[1]	44,650	45,319	44,985	45,319
Effect of nonvested phantom units		2,087		1,338
Diluted (shares)		46,737	45,319	46,323	45,319
Common unit – basic		$ 1.11	$ (0.06)	$ 1.05	$ (0.54)
Common unit – diluted		$ 1.06	$ (0.06)	$ 1.02	$ (0.54)
[1]	As a result of the GP Buy-In Transaction, our historical results are those of Summit Investments. The number of common units of 45.3 million represents those of Summit Investments and has been used for the earnings per unit calculations presented herein.

EARNINGS PER UNIT (Parenthetica

EARNINGS PER UNIT (Parenthetical) (Details) - shares	Jun. 30, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common limited partner capital (in shares), outstanding	43,543,056	45,318,866
Summit Midstream Partners Holdings L L C | Common Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common limited partner capital (in shares), outstanding	45,300,000

EARNINGS PER UNIT - Narrative (

EARNINGS PER UNIT - Narrative (Details) - Summit Midstream Partners Holdings L L C - shares	Jun. 30, 2020	Mar. 21, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
SMLP common units pledged as collateral under the SMPH Term Loan		34,604,581
Term Loan B [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
SMLP common units pledged as collateral under the SMPH Term Loan	34,600,000

UNIT-BASED AND NONCASH COMPEN_2

UNIT-BASED AND NONCASH COMPENSATION - Narrative (Details) - SMLP LTIP	1 Months Ended		6 Months Ended
	Jun. 30, 2020Directorshares	Mar. 31, 2020Director$ / sharesshares	Jun. 30, 2020shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Units remaining available	6,700,000		6,700,000
Phantom Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted units (in shares)		3,811,301
Grant date fair value (in dollars per share) | $ / shares		$ 0.55
Vesting period		3 years
Issued units (in shares)	187,500	549,450
No. of directors | Director	3	3
Units vested (in shares)			539,721
Number of authorized common units increased		15,000,000
Common units extended term		10 years

LEASES, COMMITMENTS AND CONTI_3

LEASES, COMMITMENTS AND CONTINGENCIES - Schedule of Right of Use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Right-of-use asset	$ 4,996	$ 3,580
Finance	2,253	3,159
Total	7,249	6,739
Lease liabilities, current
Operating	1,659	1,221
Finance	826	1,246
Total	2,485	2,467
Lease liabilities, noncurrent
Operating	4,120	2,513
Finance	310	676
Total	$ 4,430	$ 3,189

LEASES, COMMITMENTS AND CONTI_4

LEASES, COMMITMENTS AND CONTINGENCIES - Rent Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Lease expense	$ 937	$ 1,033	$ 1,890	$ 2,023

LEASES, COMMITMENTS AND CONTI_5

LEASES, COMMITMENTS AND CONTINGENCIES - Narrative (Details) - Maximum - Meadowlark Midstream Gathering System - Principal Owner	6 Months Ended
	Jun. 30, 2020USD ($)
Loss Contingencies [Line Items]
Coverage from pollution liability insurance policy	$ 25,000,000
Coverage from property and business interruption insurance policy	$ 200,000,000

LEASES, COMMITMENTS AND CONTI_6

LEASES, COMMITMENTS AND CONTINGENCIES - Environmental Matters (Details) - Meadowlark Midstream Gathering System $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrued environmental remediation, beginning balance	$ 4,651
Payments made	(545)
Accrued environmental remediation, ending balance	$ 4,106

DISPOSITIONS AND RESTRUCTURING

DISPOSITIONS AND RESTRUCTURING - Tioga Midstream Disposition (Details) - Tioga Midstream, LLC - Disposal, not discontinued operations $ in Millions	Mar. 22, 2019USD ($)	Feb. 28, 2019USD ($)Agreement
Business Acquisition [Line Items]
Number of purchase and sale agreements | Agreement		2
Cash purchase price of disposals		$ 90
Gain on sale of business	$ 0.9

DISPOSITIONS AND RESTRUCTURIN_2

DISPOSITIONS AND RESTRUCTURING - 2016 Drop Down (Details) - Drop Down Assets 2016 Acquisition - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Working capital adjustment	$ 0.6
Revolving credit facility
Business Acquisition [Line Items]
Cash paid to Acquire investment		$ 360

DISPOSITIONS AND RESTRUCTURIN_3

DISPOSITIONS AND RESTRUCTURING - Restructuring Activities (Details) - Employee Related Costs - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Severance costs			$ 3.3
Restructuring costs	$ 0.6	$ 3.3
Cash payment		5.7
Employee related cost included in other current liabilities	$ 0.9	$ 0.9

SUBSEQUENT EVENTS - Narrative (

SUBSEQUENT EVENTS - Narrative (Details) - USD ($) $ in Millions	Aug. 07, 2020	Jul. 28, 2020	Aug. 06, 2020	Jun. 30, 2020	Jul. 31, 2014
Summit Holdings and Finance Corporation | 5.5% Senior Notes
Subsequent Event [Line Items]
Stated interest rate				5.50%	5.50%
Senior Notes repurchased				$ 25.8
Subsequent Event
Subsequent Event [Line Items]
Conversion ratio		200
Number of shares exchanged		62,816
Number of shares issued on conversion		12,563,200
Number of shares not tendered		237,184
Subsequent Event | ECP Term Loan Credit Agreements [Member]
Subsequent Event [Line Items]
Repayments of loans	$ 35
Accrued interest on loan	$ 0.6
Subsequent Event | Summit Holdings and Finance Corporation | 5.5% Senior Notes
Subsequent Event [Line Items]
Senior Notes repurchased face amount			$ 5.9
Stated interest rate			5.50%
Weighted average discount rate			34.00%
Senior Notes repurchased			$ 3.9