Summit Midstream Partners (SMLP) 10-K 28 Feb 22 2021 FY Annual report Financial data

COVER PAGE

COVER PAGE - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 15, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-35666
Entity Registrant Name	Summit Midstream Partners, LP
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common Units
Trading Symbol	SMLP
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 204,910,000
Entity Common Stock, Shares Outstanding		10,023,709
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement relating to its 2022 Annual Meeting of Limited Partners, which will be filed with the Securities and Exchange Commission within 120 days of December 31, 2021, are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated.
Entity Central Index Key	0001549922
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY

AUDIT INFORMATION

AUDIT INFORMATION	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Location	Houston, Texas
Auditor Firm ID	34

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 7,349	$ 15,544
Restricted cash	12,223	0
Accounts receivable	62,121	61,932
Other current assets	5,676	4,623
Total current assets	87,369	82,099
Property, plant and equipment, net	1,726,082	1,813,810
Intangible assets, net	172,927	199,566
Investment in equity method investees	523,196	392,740
Other noncurrent assets	12,888	11,602
TOTAL ASSETS	2,522,462	2,499,817
LIABILITIES AND CAPITAL
Trade accounts payable	10,498	11,878
Accrued expenses	14,462	13,036
Deferred revenue	10,374	9,988
Ad valorem taxes payable	8,570	9,086
Accrued compensation and employee benefits	11,019	9,658
Accrued interest	12,737	8,007
Accrued environmental remediation	3,068	1,392
Accrued settlement payable	4,833	0
Other current liabilities	3,676	5,363
Total current liabilities	79,237	68,408
Long-term debt, net	1,355,072	1,347,326
Noncurrent deferred revenue	42,570	48,250
Noncurrent accrued environmental remediation	2,538	1,537
Other noncurrent liabilities	32,357	21,747
Total liabilities	1,511,774	1,487,268
Commitments and contingencies (Note 10)
Mezzanine Capital
Subsidiary Series A Preferred Units (91,439 and 85,308 units issued and outstanding at December 31, 2021 and December 31, 2020, respectively)	106,325	89,658
Partners Capital
Series A Preferred Units (143,447 and 162,109 units issued and outstanding at December 31, 2021 and December 31, 2020, respectively)	169,769	174,425
Common limited partner capital (7,169,834 and 6,110,092 units issued and outstanding at December 31, 2021 and December 31, 2020, respectively)	734,594	748,466
Total partners capital	904,363	922,891
TOTAL LIABILITIES AND CAPITAL	$ 2,522,462	$ 2,499,817

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Dec. 31, 2021	Dec. 31, 2020
Partners Capital
Common limited partner capital, issued (in shares)	7,169,834	6,110,092
Common limited partner capital, outstanding (in shares)	7,169,834	6,110,092
Subsidiary Series A Preferred Units
Subsidiary Series A preferred unitholders, issued (in shares)	91,439,000	85,308,000
Subsidiary Series A preferred unitholders, outstanding (in shares)	91,439,000	85,308,000
Series A Preferred Units
Subsidiary Series A preferred unitholders, issued (in shares)	143,447	162,109
Subsidiary Series A preferred unitholders, outstanding (in shares)	143,447	162,109

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Total revenues	$ 400,618	$ 383,473
Costs and expenses:
Type of Cost, Good or Service [Extensible List]	Natural Gas Liquids [Member]
Cost of natural gas and NGLs	$ 81,969	36,653
Operation and maintenance	74,178	86,030
General and administrative	58,166	73,438
Depreciation and amortization	119,076	118,132
Transaction costs	1,677	2,993
Gain on asset sales, net	(369)	(307)
Long-lived asset impairment	10,151	13,089
Total costs and expenses	344,848	330,028
Other income (expense), net	(613)	48
Loss on ECP Warrants	(13,634)	0
Interest expense	(66,156)	(78,894)
Gain (loss) on early extinguishment of debt	(3,523)	203,062
Income (loss) before income taxes and equity method investment income	(28,156)	177,661
Income tax benefit	327	146
Income from equity method investees	7,880	11,271
Net income (loss)	(19,949)	189,078
Net loss attributable to noncontrolling interest	0	3,274
Add: deemed capital contribution	8,326	110,669
Net income (loss) attributable to Summit Midstream Partners, LP	(36,616)	178,854
Series A Preferred Units
Costs and expenses:
Net income (loss) attributable to limited partners	(15,998)	(26,529)
Series A Preferred Units | Subsidiary
Costs and expenses:
Net income (loss) attributable to limited partners	(16,667)	(13,498)
Common units
Costs and expenses:
Net income (loss) attributable to limited partners	$ (44,288)	$ 262,994
Net income (loss) per limited partner unit:
Common unit - basic (in dollars per share)	$ (6.57)	$ 73.22
Common unit - diluted (in dollars per share)	$ (6.57)	$ 71.19
Weighted-average limited partner units outstanding:
Common units - basic (in shares)	6,741	3,592
Common units - diluted (shares)	6,741	3,694
Gathering services and related fees
Revenues:
Total revenues	$ 281,705	$ 302,792
Natural gas, NGLs and condensate sales
Revenues:
Total revenues	82,768	49,319
Other revenues
Revenues:
Total revenues	$ 36,145	$ 31,362

CONSOLIDATED STATEMENTS OF PART

CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	Series A Preferred UnitsNoncontrolling Interest	Common Noncontrolling InterestNoncontrolling Interest	[1]	Partners' Capital	Partners' CapitalSeries A Preferred Units
Beginning balance at Dec. 31, 2019	$ 785,236	$ 293,616	$ 186,070		$ 305,550	$ 0
Net income (loss)	175,580	11,875	(3,274)		152,325	14,654
Unit-based compensation	8,111		4,054		4,057
Tax withholdings and associated payments on vested SMLP LTIP awards	(1,456)		1,018		(438)
Tax withholdings on Series A Preferred Unit Exchange	(237)				(237)
Net cash distribution to SMLP unitholders	(6,037)		(6,037)
Effect of common issuances under  SMLP LTIP	0		2,322		(2,322)
GP-Buy-In Transaction assumption of noncontrolling interest in SMLP	0	(305,491)	(182,117)		182,117	305,491
Repurchase of common units under GP Buy-In Transaction	(44,078)				(44,078)
Common unit issuance due to TL Restructuring	30,521
Conversion of Preferred Units	(25,000)				120,720	(145,720)
Other	251				251
Ending balance at Dec. 31, 2020	922,891	0	0		748,466	174,425
Net income (loss)	(36,616)				(52,614)	15,998
Unit-based compensation	4,744				4,744
Tax withholdings and associated payments on vested SMLP LTIP awards	(1,733)				(1,733)
Tax withholdings on Series A Preferred Unit Exchange	(465)				(465)
Conversion of Preferred Units	0				20,654	(20,654)
Exercise of ECP Warrants	15,542				15,542
Ending balance at Dec. 31, 2021	$ 904,363	$ 0	$ 0		$ 734,594	$ 169,769
[1]	Prior to the GP Buy-in Transaction, common noncontrolling interests reported by Summit Investments included equity interests in SMLP that were not owned by Summit Investments.

CONSOLIDATED STATEMENTS OF PA_2

CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Statement of Partners' Capital [Abstract]
Deemed contribution to common unit holders	$ 8.3	$ 110.7

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income (loss)	$ (19,949)	$ 189,078
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	119,995	119,070
Noncash lease expense	1,104	3,242
Amortization of debt issuance costs	7,017	6,608
Unit-based and noncash compensation	4,744	8,111
Income from equity method investees	(7,880)	(11,271)
Distributions from equity method investees	26,760	28,185
Gain on asset sales, net	(369)	(307)
(Gain) loss on extinguishment of debt	3,245	(206,975)
(Gain) loss on ECP Warrants and other	13,635	(393)
Unrealized loss on interest rate swaps	779	134
Long-lived asset impairment	10,151	13,089
Changes in operating assets and liabilities:
Accounts receivable	(178)	35,352
Trade accounts payable	(89)	(4,063)
Accrued expenses	1,422	2,841
Deferred revenue, net	(5,295)	6,036
Ad valorem taxes payable	(516)	609
Accrued interest	4,730	(3,343)
Accrued environmental remediation, net	2,676	(1,996)
Other, net	3,117	14,582
Net cash provided by operating activities	165,099	198,589
Cash flows from investing activities:
Capital expenditures	(25,030)	(43,128)
Proceeds from asset sale	8,000	0
Other, net	0	2,486
Net cash used in investing activities	(165,729)	(140,569)
Cash flows from financing activities:
Borrowings under 2026 Secured Notes	689,500
Repayment of 2022 Senior Notes	(234,047)
Proceeds from Issuance of Other Long-term Debt	160,000
Proceeds under credit facilities	300,000	249,300
Repayments on ABL Facility	(33,000)
Net cash distributions to noncontrolling interest SMLP unitholders		(6,037)
Repayments on Revolving Credit Facility	(857,000)	(69,300)
Transaction costs	0	(4,221)
Repayments on SMPH Term Loan before TL Restructuring	0	(6,300)
TL Restructuring	0	(26,500)
Proceeds from issuance of Subsidiary Series A Preferred Units, net of issuance costs	0	48,710
Preferred Tender	0	(25,000)
Borrowings under ECP Loans	0	35,000
Repayment of ECP Loans	0	(35,000)
Purchase of common units in GP Buy-In Transaction	0	(41,778)
Debt issuance costs	(20,228)	(2,558)
Proceeds from asset sale	357	288
Other, net	(924)	(2,905)
Net cash used in (provided by) financing activities	4,658	(79,398)
Net change in cash, cash equivalents and restricted cash	4,028	(21,378)
Cash, cash equivalents and restricted cash, beginning of period	15,544	36,922
Cash, cash equivalents and restricted cash, end of period	19,572	15,544
Double E
Cash flows from operating activities:
Net income (loss)	(1,702)	(2,604)
Cash flows from investing activities:
Investment in Double E equity method investee	(148,699)	(99,927)
Open Market Repurchases
Cash flows from financing activities:
Repurchases of Senior Notes	0	(145,567)
Tender Offers
Cash flows from financing activities:
Repurchases of Senior Notes	$ 0	$ (47,530)

SUPPLEMENTAL CASH FLOW INFORMAT

SUPPLEMENTAL CASH FLOW INFORMATION	12 Months Ended
	Dec. 31, 2021
Supplemental Cash Flow Elements [Abstract]
SUPPLEMENTAL CASH FLOW INFORMATION	14. SUPPLEMENTAL CASH FLOW INFORMATION Year ended December 31, 2021 2020 (In thousands) Supplemental cash flow information: Cash interest paid $ 57,655 $ 79,450 Cash paid for taxes $ 191 $ 190 Noncash investing and financing activities: Capital expenditures in trade accounts payable (period-end accruals) $ 5,692 $ 6,154 Warrant issuance for GP Buy-In Transaction — 2,300 Right-of-use assets relating to ASC Topic 842 — 3,685 Fair value of SMLP equity for TL Restructuring — 30,521 Accretion of Subsidiary Series A Preferred Units 10,536 8,247 Exercise of ECP Warrants 15,542 —

ORGANIZATION, BUSINESS OPERATIO

ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION	1. ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION Organization. Summit Midstream Partners, LP (including its subsidiaries, collectively “SMLP” or the “Partnership”) is a Delaware limited partnership that 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. The Partnership’s business activities are primarily conducted through various operating subsidiaries, each of which is owned or controlled by its wholly owned subsidiary holding company, Summit Holdings, a Delaware limited liability company. As of December 31, 2021, the Partnership indirectly owns its General Partner, and the General Partner is a wholly owned, indirect subsidiary of the Partnership. The General Partner has no assets or liabilities and holds the non-economic general partner interest in the Partnership. GP Buy-In Transaction. On May 28, 2020, the Partnership closed the transactions contemplated by the Purchase Agreement (the “Purchase Agreement”), dated May 3, 2020, with affiliates of its then private equity sponsor, Energy Capital Partners II, LLC (“ECP”), to acquire Summit Investments. The acquisition of Summit Investments resulted in the Partnership acquiring (a) 2.3 million SMLP common units that were pledged as collateral under the SMPH Term Loan, (b) 0.7 million SMLP common units that were not pledged as collateral under the SMPH Term Loan and (c) a deferred purchase price obligation receivable owed by the Partnership. In addition, the Partnership acquired 0.4 million SMLP common units held by an affiliate of ECP. The total purchase price was $35.0 million in cash and warrants giving ECP the right to purchase up to 0.7 million SMLP common units (refer to Note 12 – Partners’ Capital and Mezzanine Capital for additional details). Pursuant to the Purchase Agreement, the Partnership retained any liabilities stemming from the release of produced water from a produced water pipeline operated by Meadowlark Midstream, a subsidiary of the Partnership, that occurred near Williston, North Dakota and was discovered on January 6, 2015. These transactions are collectively referred to as the “GP Buy-In Transaction.” As a result of the GP Buy-In Transaction, the Partnership indirectly owns its General Partner. Following the closing of the GP Buy-In Transaction, the Partnership retired 1.1 million SMLP common units it acquired that were not pledged as collateral under the SMPH Term Loan. The 2.3 million SMLP common units that were pledged as collateral under the SMPH Term Loan were not considered outstanding with respect to voting and distributions under the Partnership Agreement until the closing of the TL Restructuring on November 17, 2020 (refer to Note 9 -Liability Management Transactions). 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. Reverse Unit Split. On November 9, 2020, after the close of trading on the NYSE, the Partnership effected a 1-for-15 reverse unit split (the “Reverse Unit Split”) of its common units. The common units began trading on a split-adjusted basis on November 10, 2020. Pursuant to the Reverse Unit Split, common unitholders received one common unit for every 15 common units owned at the close of business on November 9, 2020. Immediately prior to the Reverse Unit Split, there were 56,624,887 common units issued and outstanding and immediately after the Reverse Unit Split, the number of issued and outstanding common units decreased to 3,774,992. Business Operations. The Partnership provides 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 its customers. The Partnership’s results are primarily driven by the volumes of natural gas that it gathers, compresses, treats and/or processes as well as by the volumes of crude oil and produced water that it gathers. Other than the Partnership’s investments in Double E and Ohio Gathering, all of its business activities are conducted through wholly owned operating subsidiaries. Presentation and Consolidation. The Partnership prepares its consolidated financial statements in accordance with GAAP as established by the FASB. The Partnership makes 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. Although management believes these estimates are reasonable, actual results could differ from its estimates. The consolidated financial statements include the assets, liabilities and results of operations of SMLP and its subsidiaries. All intercompany transactions among the consolidated entities have been eliminated in consolidation. Comprehensive income or loss is the same as net income or loss for all periods presented. Risks and Uncertainties. The Partnership continues to closely monitor the impact of the COVID-19 pandemic on all aspects of its business, including how it has impacted and will impact its customers, employees, supply chain and distribution network. The Partnership is unable to predict the ultimate impact that COVID-19 may have on its business, future results of operations, financial position or cash flows. Given the dynamic nature of the COVID-19 pandemic and related market conditions, the Partnership cannot reasonably estimate the period of time that these events will persist or the full extent of the impact they will have on its business. The full extent to which the Partnership’s 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 development and availability of treatments and vaccines and the extent to which these treatments and vaccines may remain effective as potential new strains of the coronavirus emerge. 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	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENTLY ISSUED ACCOUNTING STANDARDS APPLICABLE TO THE PARTNERSHIP Cash, Cash Equivalents and Restricted Cash. The Partnership considers 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 the Partnership is classified as restricted cash. The restricted cash balance of $12.2 million at December 31, 2021 is related to proceeds which are available to finance Permian Transmission’s capital calls associated with its investment in Double E, for debt service or other general corporate purposes of Permiam Transmission. See Note 8 - Debt for additional information. Accounts Receivable. Accounts receivable relate to gathering and other services provided to the Partnership’s customers and other counterparties. The Partnership evaluates the collectability of accounts receivable and the need for an allowance for doubtful accounts based on customer-specific facts and circumstances. To the extent the collectability of a specific customer or counterparty receivable is doubtful, the Partnership recognizes an allowance for doubtful accounts. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable. Property, Plant and Equipment. The Partnership records property, plant and equipment at historical cost of construction or fair value of the assets at acquisition. The Partnership capitalizes expenditures that extend the useful life of an asset or enhance its productivity or efficiency from its original design over the expected remaining period of use. For maintenance and repairs that do not add capacity or extend the useful life of an asset, the Partnership recognizes expenditures as an expense as incurred. The Partnership capitalizes project costs incurred during construction, including interest on funds borrowed to finance the construction of facilities, as construction in progress. Accrued capital expenditures are reflected in trade accounts payable. The Partnership records depreciation on a straight-line basis over an asset’s estimated useful life and bases its estimates for useful life on various factors including age (in the case of acquired assets), manufacturing specifications, technological advances and historical data concerning useful lives of similar assets. Estimates of useful lives follow. Useful lives (In years) Gathering and processing systems and related equipment 12-30 Other 4-15 Construction in progress is depreciated consistent with its applicable asset class once it is placed in service. Land and line fill are not depreciated. The Partnership bases an asset’s carrying value on estimates, assumptions and judgments for useful life and salvage value. Upon sale, retirement or other disposal, the Partnership removes the carrying value of an asset and its accumulated depreciation from its balance sheet and recognizes the related gain or loss, if any. Asset Retirement Obligations. The Partnership records a liability for asset retirement obligations only if and when a future asset retirement obligation with a determinable life is identified. For identified asset retirement obligations, the Partnership evaluates whether the expected retirement date and related costs of retirement can be estimated. The Partnership has concluded that its gathering and processing assets have an indeterminate life because they are owned and will operate for an indeterminate period when properly maintained. Because the Partnership does not have sufficient information to reasonably estimate the amount or timing of such obligations and does not have any current plan to discontinue use of any significant assets, the Partnership did not provide for any asset retirement obligations as of December 31, 2021 or 2020. Amortizing Intangibles. The Partnership has certain acquired gas gathering contracts that had above-market pricing structures at the acquisition date and the Partnership amortizes these favorable contracts using a straight-line method over the contract’s estimated useful life. The Partnership defines useful life as the period over which the contract is expected to contribute to the Partnership’s future cash flows. These favorable contracts have original terms ranging from 10 years to 20 years and the Partnership recognizes the amortization expense associated with these contracts in Other revenues. The Partnership amortizes all other gas gathering contracts, or contract intangibles, over the period of economic benefit based upon expected revenues over the life of the contract. The useful life of these contracts ranges from 3 years to 25 years. The Partnership recognizes the amortization expense associated with these contracts in Depreciation and amortization expense. The Partnership also has rights-of-way associated with municipal easements and easements granted within existing rights-of-way. The Partnership amortizes these intangible assets over the shorter of the contractual term of the rights-of-way or the estimated useful life of the gathering system. The contractual terms of the rights-of-way range from 20 years to 30 years and the Partnership recognizes the amortization expense associated with these rights-of-way assets in Depreciation and amortization expense. Equity Method Investments. The Partnership accounts for investments in which it exercises significant influence using the equity method so long as it (i) does not control the investee and (ii) is not the primary beneficiary. The Partnership reflects these investments in its consolidated balance sheets under the caption titled “investment in equity method investees.” The Partnership recognizes an other-than-temporary impairment for losses in the value of equity method investees when evidence indicates that the carrying amount is no longer supportable. Evidence of a loss in value might include, but is not limited to, absence of an ability to recover the carrying amount of the investment or an inability of the equity method investee to sustain an earnings capacity that would justify the carrying amount of the investment. A current fair value of an investment that is less than its carrying amount may indicate a loss in value of the investment. The Partnership evaluates its equity method investments whenever a triggering event exists that would indicate a need to assess the investment for potential impairment. Impairment of Long-Lived Assets. The Partnership tests assets for impairment when events or circumstances indicate the carrying value of a long-lived asset may not be recoverable. The carrying value of a long-lived asset (except goodwill) is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from its use and eventual disposition. If the Partnership concludes that an assets carrying value will not be recovered through future cash flows, the Partnership recognizes an impairment loss on the long-lived asset equal to the amount by which the carrying value exceeds its fair value. The Partnership determines fair value using a combination of market-based and income-based approaches. Environmental Matters. The Partnership is subject to various federal, state and local laws and regulations relating to the protection of the environment. Liabilities for loss contingencies, including environmental remediation costs, arising from claims, assessments, litigation, fines and penalties and other sources are charged to expense when it is probable that a liability has been incurred and the amount of the assessment and/or remediation can be reasonably estimated. The Partnership accrues for losses associated with environmental remediation obligations when such losses are probable and reasonably estimable. Such accruals are adjusted as further information develops or circumstances change. Recoveries of environmental remediation costs from other parties or insurers are recorded as assets when their realization is assured beyond a reasonable doubt. Commitments and Contingencies. When required, the Partnership records accruals for loss contingencies in accordance with FASB ASC 450, Contingencies . Such determinations are subject to interpretations of current facts and circumstances, forecasts of future events and estimates of the financial impacts of such events. Noncontrolling Interest and Mezzanine Capital . A noncontrolling interest represents the portion of a consolidated subsidiary that is owned by a third party. Amounts are adjusted by the noncontrolling interest holder’s proportionate share of the subsidiary’s earnings or losses each period and any distributions that are paid. A noncontrolling interest is reported as a component of equity unless the noncontrolling interest is considered redeemable, in which case the noncontrolling interest is recorded between liabilities and equity (mezzanine or temporary equity) in the Partnership’s consolidated balance sheet. Revenue. The Partnership provides gathering and/or processing services principally under contracts that contain one or more of the following arrangements described below: • Fee-based arrangements. Under fee-based arrangements, the Partnership receives a fee or fees for one or more of the following services (i) natural gas gathering, treating, transporting, compressing and/or processing and (ii) crude oil and/or produced water gathering. • Percent-of-proceeds arrangements. Under percent-of-proceeds arrangements, the Partnership generally purchases natural gas from producers at the wellhead, or other receipt points, gathers the wellhead natural gas through its gathering system, treats and compresses the natural gas, processes the natural gas and/or sells the natural gas to a third party for processing. The Partnership then remits to its producers an agreed-upon percentage of the actual proceeds received from sales of the residue natural gas and NGLs. Certain of these arrangements may also result in returning all or a portion of the residue natural gas and/or the NGLs to the producer, in lieu of returning sales proceeds. The margins earned are directly related to the volume of natural gas that flows through the system and the price at which the Partnership is able to sell the residue natural gas and NGLs. The majority of the Partnership’s contracts have a single performance obligation which is either to provide gathering services (an integrated service) or sell natural gas, NGLs and condensate, which are both satisfied when the related natural gas, crude oil and produced water are received and transferred to an agreed upon delivery point. The Partnership also has certain contracts with multiple performance obligations. They include an option for the customer to acquire additional services such as contracts containing MVCs. These performance obligations would also be satisfied when the related natural gas, crude oil and produced water are received and transferred to an agreed upon delivery point. In these instances, the Partnership allocates the contract’s transaction price to each performance obligation using its best estimate of the standalone selling price of each service in the contract. Performance obligations for gathering services are generally satisfied over time. The Partnership utilizes either an output method (i.e., measure of progress) for guaranteed, stand-ready service contracts or an asset/system delivery time estimate for non-guaranteed, as-available service contracts. Performance obligations for the sale of natural gas, NGLs and condensate are satisfied at a point in time. There are no significant judgments for these transactions because the customer obtains control based on an agreed upon delivery point. Services are typically billed on a monthly basis and the Partnership does not offer extended payment terms. The Partnership does not have contracts with financing components. For the contracts described above, the Partnership reflects its revenues in the financial statement captions described below. Financial statement caption: Revenue description: Revenues: Gathering services and related fees • Revenue earned from fee-based gathering, compression, treating and processing services; Natural gas, NGLs and condensate sales • Revenue from the sale of physical natural gas purchased from customers percent-of- proceeds arrangements (Costs are presented within cost of natural gas and NGLs); • Revenue from sale of condensate and NGLs retained from gathering services (Costs are presented within operation and maintenance expense); and Other revenues • Customer reimbursements to the Partnership for costs incurred by the Partnership on customer’s behalf (Recorded on a gross basis). Certain of the Partnership’s gathering and/or processing agreements provide for monthly or annual MVCs. Under these MVCs, customers agree to ship and/or process a minimum volume of production on its gathering systems or to pay a minimum monetary amount over certain periods during the term of the MVC. A customer must make a shortfall payment to the Partnership at the end of the contracted measurement period if its actual throughput volumes are less than its contractual MVC for that period. Certain customers are entitled to utilize shortfall payments to offset gathering fees in one or more subsequent contracted measurement periods to the extent that such customers throughput volumes in a subsequent contracted measurement period exceed its MVC for that contracted measurement period. The Partnership recognizes customer obligations under their MVCs as revenue and contract assets when (i) it considers it remote that the customer will utilize shortfall payments to offset gathering or processing fees in excess of its MVCs in subsequent periods; (ii) the customer incurs a shortfall in a contract with no banking mechanism or claw back provision; (iii) the customer’s banking mechanism has expired; or (iv) it is remote that the customer will use its unexercised right. In making this determination, the Partnership considers both quantitative and qualitative facts and circumstances, including, but not limited to, contract terms, capacity of the associated pipeline or receipt point and/or expectations regarding future investment, drilling and production. The majority of the Partnership’s revenue is derived from long-term, fee-based contracts with its customers, which include original terms of up to 25 years. The Partnership recognizes revenue earned from fee-based gathering, compression, treating and processing services in gathering services and related fees. The Partnership also earns revenue in the Rockies, Piceance and Permian reporting segments from the sale of physical natural gas purchased from its customers under certain percent-of- proceeds arrangements. Under ASC Topic 606, these gathering contracts are presented net within cost of natural gas and NGLs. The Partnership sells natural gas that it retains from certain customers in the Barnett reporting segment to offset the power expenses of the electric-driven compression on the DFW Midstream system. The Partnership also sells condensate and NGLs retained from certain of its gathering services in the Piceance and Permian 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 the Partnership for costs incurred on their behalf. The Partnership records costs incurred and reimbursed by its customers on a gross basis, with the revenue component recognized in Other revenues. The transaction price in the Partnership’s contracts is primarily based on the volume of natural gas, crude oil or produced water transferred by its gathering systems to the customer’s agreed upon delivery point multiplied by the contractual rate. For contracts that include MVCs, variable consideration up to the MVC will be included in the transaction price. For contracts that do not include MVCs, the Partnership does not estimate variable consideration because the performance obligations are completed and settled on a daily basis. For contracts containing noncash consideration such as fuel received in-kind, the Partnership measures the transaction price at the point of sale when the volume, mix and market price of the commodities are known. The Partnership has contracts with MVCs that are variable and constrained. Contracts with longer than monthly MVCs are reviewed on a quarterly basis and adjustments to those estimates are made during each respective reporting period, if necessary. The transaction price is allocated if the contract contains more than one performance obligation such as contracts that include MVCs. The transaction price allocated is based on the MVC for the applicable measurement period. Unit-Based Compensation. For awards of unit-based compensation, the Partnership determines a grant date fair value and recognizes the related compensation expense in the statements of operations over the vesting period for each respective award. Income Taxes. The Partnership is generally not subject to federal and state income taxes, except as noted below. However, its unitholders are individually responsible for paying federal and state income taxes on their share of its taxable income. Net income or loss for GAAP purposes may differ significantly from taxable income reportable to its unitholders as a result of differences between the tax basis and the GAAP basis of assets and liabilities and the taxable income allocation requirements of the Partnership’s governing documents. The aggregate difference in the basis of the Partnership’s net assets for financial and income tax purposes cannot be readily determined as the Partnership does not have access to the information about each partner’s tax attributes related to the Partnership. In general, legal entities that are chartered, organized or conducting business in the state of Texas are subject to a franchise tax (the “Texas Margin Tax”). The Texas Margin Tax has the characteristics of an income tax because it is determined by applying a tax rate to a tax base that considers both revenues and expenses. The Partnership’s financial statements reflect provisions for these tax obligations. Interest Rate Swaps. Interest rate swap agreements are reported as either assets or liabilities on the consolidated balance sheet at fair value. Interest rate swap agreements are not designated as cash-flow hedges, and accordingly, the changes in the fair value are recorded in earnings. The Partnership does not use interest rate swap agreements for speculative purposes. Reclassifications. Certain reclassifications have been made to prior period amounts to conform to current period financial statement presentation. These reclassifications had no effect on the consolidated financial position, results of operations or cash flows of the Partnership. New accounting standards implemented in this Annual Report. 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 the Partnership’s consolidated financial statements or 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 the Partnership’s consolidated financial statements or disclosures. New accounting standards not yet implemented in this Annual Report. ASU No. 2020-6 Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815 – 40) (“ASU 2020-6”). ASU 2020-6 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. The ASU is part of the FASB’s simplification initiative, which aims to reduce unnecessary complexity in GAAP. The ASU’s amendments are effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years. The Partnership is currently evaluating the provisions of ASU 2020-6 to determine its impact on the Partnership’s consolidated financial statements and disclosures. ASU No. 2020-4 Reference Rate Reform (“ASU 2020-4”). ASU 2020-4 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 2020-4 are effective as of March 12, 2020 through December 31, 2022. The Partnership is currently evaluating the provisions of ASU 2020-4 to determine its impact on the Partnership’s consolidated financial statements and disclosures.

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
REVENUE	3. REVENUE The following table presents estimated revenue expected to be recognized over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated MVC shortfall payments. The Partnership applies the practical expedient in paragraph 606-10-50-14 of Topic 606 for certain arrangements that are considered optional purchases (i.e., there is no enforceable obligation for the customer to make purchases) and those amounts are therefore excluded from the table. 2022 2023 2024 2025 2026 Thereafter Gathering services and related fees $ 81,722 $ 63,214 $ 52,412 $ 35,805 $ 21,024 $ — Revenue by Category . In the following table, revenue is disaggregated by geographic area and major products and services. For more detailed information about reportable segments, see Note 18 -Segment Information. Year ended December 31, 2021 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (in thousands) Reportable Segments: Northeast $ 62,567 $ — $ — $ 62,567 Rockies 74,823 48,279 21,985 145,087 Permian 8,230 28,727 3,891 40,848 Piceance 95,235 5,464 4,786 105,485 Barnett 40,850 298 5,443 46,591 Total reportable segments 281,705 82,768 36,105 400,578 Corporate and other — — 40 40 Total $ 281,705 $ 82,768 $ 36,145 $ 400,618 Year ended December 31, 2020 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (in thousands) Reportable Segments: Northeast $ 62,250 $ — $ — $ 62,250 Rockies 83,107 20,263 17,395 120,765 Permian 10,091 18,857 3,161 32,109 Piceance 106,657 2,612 4,621 113,890 Barnett 40,687 7,587 6,185 54,459 Total reportable segments 302,792 49,319 31,362 383,473 Corporate and other — — — — Total $ 302,792 $ 49,319 $ 31,362 $ 383,473 Contract balances . Contract assets relate to the Partnership’s rights to consideration for work completed but not billed at the reporting date and consist of 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 : December 31, 2021 December 31, 2020 (In thousands) Contract assets, beginning balance $ 2,026 $ 3,902 Additions 9,274 18,834 Transfers out (973) (20,710) Contract assets, ending balance $ 10,327 $ 2,026 As of December 31, 2021, receivables with customers totaled $50.5 million and contract assets totaled $10.3 million which were included in the Accounts receivable caption on the consolidated balance sheet. As of December 31, 2020, receivables with customers totaled $57.5 million and contract assets totaled $2.0 million which were included in the Accounts receivable caption on the consolidated balance sheet.

PROPERTY, PLANT, AND EQUIPMENT

PROPERTY, PLANT, AND EQUIPMENT	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT, AND EQUIPMENT	4. PROPERTY, PLANT AND EQUIPMENT Details on the Partnership’s property, plant and equipment follow. December 31, 2021 December 31, 2020 (In thousands) Gathering and processing systems and related equipment $ 2,225,267 $ 2,213,501 Construction in progress 49,082 60,443 Land and line fill 10,644 10,440 Other 51,863 51,276 Total 2,336,856 2,335,660 Less accumulated depreciation (610,774) (521,850) Property, plant and equipment, net $ 1,726,082 $ 1,813,810 When the carrying amount of a long-lived asset is not recoverable, an impairment is recognized equal to the excess of the asset’s carrying value over its fair value, which is based on inputs that are not observable in the market, and thus represent Level 3 inputs under GAAP’s fair value hierarchy. The Partnership recognized $10.2 million and $13.1 million of impairments during the fiscal years ended December 31, 2021 and 2020, respectively. Due to the volatility of the inputs used, the Partnership cannot predict the likelihood of any future impairment. Depreciation expense and capitalized interest for the Partnership follow. Year ended December 31, 2021 2020 (In thousands) Depreciation expense $ 90,711 $ 86,263 Capitalized interest 1,534 $ 3,878

AMORTIZING INTANGIBLE ASSETS

AMORTIZING INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
AMORTIZING INTANGIBLE ASSETS	5. AMORTIZING INTANGIBLE ASSETS Details regarding the Partnership’s intangible assets, all of which are subject to amortization, follow. December 31, 2021 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (17,002) $ 7,193 Contract intangibles 278,448 (217,245) 61,203 Rights-of-way 159,916 (55,385) 104,531 Total intangible assets $ 462,559 $ (289,632) $ 172,927 December 31, 2020 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (16,064) $ 8,131 Contract intangibles 278,448 (195,243) 83,205 Rights-of-way 157,271 (49,041) 108,230 Total intangible assets $ 459,914 $ (260,348) $ 199,566 The Partnership recognized amortization expense of its favorable gas gathering contracts in Other revenues as follows: Year ended December 31, 2021 2020 (In thousands) Amortization expense – favorable gas gathering contracts $ 938 $ 938 The Partnership recognized amortization expense of its contract and right of way intangibles in costs and expenses as follows: Year ended December 31, 2021 2020 (In thousands) Amortization expense – contract intangibles $ 22,002 $ 25,694 Amortization expense – rights-of-way 6,344 6,175 The Partnership’s estimated aggregate annual amortization expected to be recognized as of December 31, 2021 for each of the five succeeding fiscal years follows. (In thousands) 2022 $ 25,466 2023 25,412 2024 15,241 2025 15,057 2026 12,034 Thereafter 79,717 $ 172,927

EQUITY METHOD INVESTMENTS

EQUITY METHOD INVESTMENTS	12 Months Ended
	Dec. 31, 2021
Equity Method Investments and Joint Ventures [Abstract]
EQUITY METHOD INVESTMENTS	6. EQUITY METHOD INVESTMENTS The Partnership has equity method investments in Double E and Ohio Gathering, the balances of which are included in the Investment in equity method investees caption on the consolidated balance sheets. Details of the Partnership’s equity method investments follows. December 31, 2021 December 31, 2020 (In thousands) Double E $ 280,952 $ 132,852 Ohio Gathering 242,244 259,888 Total $ 523,196 $ 392,740 Double E. The Partnership, through its wholly-owned subsidiary Summit Permian Transmission, LLC, has a 70% ownership in Double E Pipeline, LLC (the “Double E”). Double E owns a long-haul natural gas pipeline (the “Double E Pipeline”) that provides transportation service for residue natural gas from multiple receipt points in the Delaware Basin to various delivery points in and around the Waha hub in Texas. The Double E Pipeline commenced operations in November 2021 and during the years ended December 31, 2021 and 2020, the Partnership made cash investments of $148.7 million and $99.9 million, respectively, in Double E, with such amounts including $3.0 million and $2.7 million of capitalized interest, respectively. Double E is deemed to be a variable interest entity as defined in GAAP. Summit Permian Transmission was not deemed to be the primary beneficiary of Double E due to the voting rights of Double E’s other owner regarding significant matters. The Partnership accounts for its ownership interest in Double E as an equity method investment because it has significant influence over Double E. For the years ended December 31, 2021 and 2020, other than the investment activity noted above, Double E did not have any material results of operations given that the Double E Pipeline commenced operations in November 2021. At December 31, 2021 and 2020, the Partnership’s carrying amount of its interest in Double E approximated its underlying investment. Summarized balance sheet information for Double E follows (amounts represent 100% of investee financial information). December 31, 2021 December 31, 2020 (In thousands) Current assets $ 12,353 $ 3,060 Noncurrent assets 410,731 197,463 Total assets $ 423,084 $ 200,523 Current liabilities $ 22,836 $ 12,479 Noncurrent liabilities 10,281 4,452 Total liabilities $ 33,117 $ 16,931 Summarized statements of operations information for Double E follows (amounts represent 100% of investee financial information). Year ended December 31, 2021 Year Ended December 31, 2020 (In thousands) Total revenues $ 3,579 $ — Total operating expenses 5,281 2,604 Net income (loss) $ (1,702) $ (2,604) Ohio Gathering. The Partnership has investments in OGC and OCC that it collectively refers to as Ohio Gathering. Ohio Gathering owns, operates and is currently developing 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. The Partnership made its initial investment in Ohio Gathering in 2014 and owned approximately 38% of Ohio Gathering at December 31, 2021 and 2020. Ohio Gathering is accounted for as an equity method investment because it has joint control with non-affiliated owners, which gives the Partnership significant influence. A reconciliation of the difference between the carrying amount of the Partnership’s interest in Ohio Gathering and the Partnership’s underlying investment in Ohio Gathering, per Ohio Gathering’s books and records, is shown below. 2021 2020 (In thousands) Investment in Ohio Gathering, December 31 $ 242,244 $ 259,888 December cash distributions 2,222 2,748 Impairment loss 1,971 — Basis difference 207,927 216,591 Other 137 — Investment in Ohio Gathering (Books and records), November 30, $ 454,501 $ 479,227 Summarized balance sheet information for OGC and OCC follows (amounts represent 100% of investee financial information). November 30, 2021 November 30, 2020 OGC OCC OGC OCC (In thousands) Current assets $ 36,967 $ 5,300 $ 32,404 $ 4,902 Noncurrent assets 1,189,921 961 1,240,090 290 Total assets $ 1,226,888 $ 6,261 $ 1,272,494 $ 5,192 Current liabilities $ 7,984 $ 3,104 $ 8,424 $ 2,982 Noncurrent liabilities 9,854 4,927 8,441 5,146 Total liabilities $ 17,838 $ 8,031 $ 16,865 $ 8,128 Summarized statements of operations information for OGC and OCC follows (amounts represent 100% of investee financial information). Twelve months ended Twelve months ended OGC OCC OGC OCC (In thousands) Total revenues $ 102,140 $ 12,614 $ 114,524 $ 12,931 Total operating expenses 95,399 11,419 103,020 38,502 Net income (loss) 6,742 1,169 11,496 (25,571)

DEFERRED REVENUE

DEFERRED REVENUE	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
DEFERRED REVENUE	7. DEFERRED REVENUE Certain of the Partnership’s gathering and/or processing agreements provide for monthly or annual MVCs. The amount of the shortfall payment is based on the difference between the actual throughput volume shipped and/or processed for the applicable period and the MVC for the applicable period, multiplied by the applicable gathering or processing fee. Many of the Partnership’s gas gathering agreements contain provisions that can reduce or delay the cash flows that it expects to receive from MVCs to the extent that a customer's actual throughput volumes are above or below its MVC for the applicable contracted measurement period. These provisions include the following: • To the extent that a customer's throughput volumes are less than its MVC for the applicable period and the customer makes a shortfall payment, it may be entitled to an offset in one or more subsequent periods to the extent that its throughput volumes in subsequent periods exceed its MVC for those periods. In such a situation, the Partnership would not receive gathering fees on throughput in excess of that customer's MVC (depending on the terms of the specific gas gathering agreement) to the extent that the customer had made a shortfall payment with respect to one or more preceding measurement periods (as applicable). • To the extent that a customer's throughput volumes exceed its MVC in the applicable contracted measurement period, it may be entitled to apply the excess throughput against its aggregate MVC, thereby reducing the period for which its annual MVC applies. As a result of this mechanism, the weighted-average remaining period for which the Partnership’s MVCs apply will be less than the weighted-average of the originally stated MVC contractual terms. • To the extent that certain of the Partnership’s customers' throughput volumes exceed its MVC for the applicable period, there is a crediting mechanism that allows the customer to build a bank of credits that it can utilize in the future to reduce shortfall payments owed in subsequent periods, subject to expiration if there is no shortfall in subsequent periods. The period over which this credit bank can be applied to future shortfall payments varies, depending on the particular gas gathering agreement. The balances in deferred revenue as of December 31, 2021 and 2020 are primarily related to contributions in aid of construction which will be recognized as revenue over the life of the contract. A rollforward of current deferred revenue follows. (In thousands) Current deferred revenue, January 1, 2021 $ 9,988 Additions 6,956 Less: revenue recognized (6,570) Current deferred revenue, December 31, 2021 $ 10,374 A rollforward of noncurrent deferred revenue follows. (In thousands) Noncurrent deferred revenue, January 1, 2021 $ 48,250 Additions 1,304 Less: reclassification to current deferred revenue (6,984) Noncurrent deferred revenue, December 31, 2021 $ 42,570

DEBT

DEBT	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
DEBT	8. DEBT Debt for the Partnership at December 31, 2021 and 2020 follows. December 31, 2021 December 31, 2020 (In thousands) Revolving Credit Facility : Summit Holdings' variable rate senior secured revolving credit facility due May 13, 2022 (1) $ — $ 857,000 ABL Facility : Summit Holdings' asset based credit facility due May 1, 2026 267,000 — Permian Transmission Credit Facility : Permian Transmission's variable rate senior secured credit facility due March 8, 2028 160,000 — 2022 Senior Notes : Summit Holdings' 5.5% senior unsecured notes due August 15, 2022 (2) — 234,047 2025 Senior Notes : Summit Holdings' 5.75% senior unsecured notes due April 15, 2025 259,463 259,463 2026 Secured Notes : Summit Holdings' and Finance Corp's 8.50% senior unsecured second lien notes due October 15, 2026 700,000 — Less: unamortized debt discount and debt issuance costs (31,391) (3,184) Total long-term debt $ 1,355,072 $ 1,347,326 _______________________________________ (1) The Revolving Credit Facility was repaid in full in November 2021. (2) The 2022 Senior Notes were repaid in full in November 2021. The aggregate amount of Partnership’s debt maturing during each of the years after December 31, 2021 are as follows (in thousands): 2022 $ — 2023 — 2024 — 2025 259,463 2026 967,000 Thereafter 160,000 Total long-term debt $ 1,386,463 Revolving Credit Facility. The Partnership’s subsidiary, Summit Holdings, had a senior secured revolving credit facility (the “Revolving Credit Facility”) which allowed for revolving loans, letters of credit and swingline loans. On November 2, 2021, a portion of the proceeds from the issuance of the 2026 Secured Notes, as described below, together with cash on hand and borrowings under the ABL Facility, as defined below, was used to repay, in full, the obligations under the Revolving Credit Facility. ABL Facility. Concurrently with the issuance of the 2026 Secured Notes, on November 2, 2021, Summit Holdings, as borrower, entered into a first-lien, senior secured credit agreement, with the Partnership, the subsidiaries party thereto, Bank of America, N.A., as agent, and the several lenders and other agents party thereto, consisting of a $400.0 million asset-based revolving credit facility (the “ABL Facility”), subject to a borrowing base comprised of a percentage of eligible accounts receivable of Summit Holdings and its subsidiaries that guarantee the ABL Facility (collectively, the “ABL Facility Subsidiary Guarantors”) and a percentage of eligible above-ground fixed assets including eligible compression units, processing plants, compression stations and related equipment of Summit Holdings and the ABL Facility Subsidiary Guarantors. As of December 31, 2021, the most recent borrowing base determination of eligible assets totaled $691.2 million, an amount greater than the $400.0 million of aggregate commitments. As of December 31, 2021, the applicable margin under the adjusted LIBOR borrowings was 3.25%, the interest rate was 3.38% and the unused portion of the ABL Facility totaled $109.1 million after giving effect to the issuance of $23.9 million in outstanding but undrawn irrevocable standby letters of credit. Summit Holdings entered into that certain Loan and Security Agreement governing the ABL Facility (the “ABL Agreement”), dated as of November 2, 2021, by and among Summit Holdings, as borrower, the Partnership, the ABL Facility Subsidiary Guarantors, Bank of America, N.A., as agent, ING Capital LLC, Royal Bank of Canada and Regions Bank, as co-syndication agents, and Bank of America, N.A., ING Capital LLC, RBC Capital Markets and Regions Capital Markets, as joint lead arrangers and joint bookrunners. The ABL Facility will mature on May 1, 2026; provided that, (a) if the outstanding amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date (as defined in the ABL Agreement)) on such date equals or exceeds $50,000,000, then the ABL Facility will mature on December 13, 2024 and (b) if both (i) any amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date) is outstanding on such date and (ii) Liquidity (as defined in the ABL Agreement) is less than an amount equal to the sum of the then aggregate outstanding principal amount of the 2025 Senior Notes (or any permitted refinancing indebtedness in respect thereof that has a final maturity, scheduled amortization or any other scheduled repayment, mandatory prepayment, mandatory redemption or sinking fund obligation prior to the date that is 120 days after the Termination Date) plus the Threshold Amount (as defined in the ABL Agreement) on such date, then the ABL Facility will mature on January 14, 2025. The ABL Facility (together with certain Secured Bank Product Obligations (as defined in the ABL Agreement)) will be jointly and severally guaranteed, on a senior first-priority secured basis (subject to permitted liens), by the Partnership, Summit Holdings and each of the ABL Facility Subsidiary Guarantors. The ABL Facility restricts, among other things, Summit Holdings’ and its Restricted Subsidiaries’ (as defined in the ABL Agreement) ability and the ability of certain of their subsidiaries to: (i) incur additional debt or issue preferred stock; (ii) make distributions or repurchase equity; (iii) make payments on or redeem junior lien, unsecured or subordinated indebtedness; (iv) create liens or other encumbrances; (v) make investments, loans or other guarantees; (vi) engage in transactions with affiliates; and (viii) make acquisitions or merge or consolidate with another entity. These covenants are subject both to a number of important exceptions and qualifications. The ABL Facility requires that Summit Holdings not permit (i) the First Lien Net Leverage Ratio (as defined in the ABL Agreement) as of the last day of any fiscal quarter to be greater than 2.50:1.00, or (ii) the Interest Coverage Ratio (as defined in the ABL Agreement) as of the last day of any fiscal quarter to be less than 2.00:1.00. As of December 31, 2021, the First Lien Net Leverage Ratio was 1.10:1.00 and the Interest Coverage Ratio was 4.30:1.00 . The ABL Facility contains certain events of default customary for instruments of this type. In the case of an event of default arising from certain events of bankruptcy, insolvency or reorganization with respect to Summit Holdings, all outstanding Obligations (as defined in the ABL Agreement) will become due and payable immediately without further action or notice and all commitments under the ABL Facility will terminate. Pursuant to the ABL Agreement, the Obligations (as defined in the ABL Agreement) are (or, subject to post-closing periods for certain types of collateral, will be) generally secured by a first priority lien on and security interest in (subject to permitted liens), subject to certain exclusions and limitations set forth in the ABL Agreement, (i) substantially all of the personal property of Summit Holdings and the ABL Facility Subsidiary Guarantors, (ii) all equity interests in Summit Holdings and certain other entities, all debt securities and certain rights related to the foregoing, in each case, owned by the Partnership, (iii) Closing Date Material Gathering Station Real Property and Closing Date Pipeline Material Gathering Station Real Property (each, as defined in the ABL Agreement) and certain other material real property interests (including improvements thereon) of Summit Holdings and the ABL Facility Subsidiary Guarantors as provided in the ABL Agreement and (iv) all proceeds of the foregoing collateral . Intercreditor Agreement. On November 2, 2021, in connection with the entry into the ABL Facility and issuance of the 2026 Secured Notes, Summit Holdings and the other guarantors party thereto entered into an Intercreditor Agreement (the “Intercreditor Agreement”) with Bank of America, N.A., as first lien representative and collateral agent for the initial first lien claimholders, Regions Bank, as second lien representative for the initial second lien claimholders and collateral agent for the initial second lien claimholders, establishing (i) a first-priority lien (subject to permitted liens) status for the liens on the collateral securing the ABL Facility and any additional first-lien indebtedness and (ii) a junior priority lien (subject to permitted liens) status for the liens on the collateral securing the 2026 Secured Notes and any additional second-lien indebtedness. Permian Transmission Credit Facility. On March 8, 2021 (the “Permian Closing Date”), the Partnership’s unrestricted subsidiary, Permian Transmission, entered into a Credit Agreement which allows for $175.0 million of senior secured credit facilities (the “Permian Transmission Credit Facilities”), including a $160.0 million Term Loan Facility and a $15.0 million Working Capital Facility. The Permian Transmission Credit Facilities can be used to finance Permian Transmission’s capital calls associated with its investment in Double E, debt service and other general corporate purposes. Unexpended proceeds from draws on the Permian Transmission Credit Facilities are classified as restricted cash on the accompanying unaudited condensed consolidated balance sheets. As of December 31, 2021, the applicable margin under adjusted LIBOR borrowings was 2.375%, the interest rate was 2.5% and the unused portion of the Permian Transmission Credit Facilities totaled $13.0 million, subject to a commitment fee of 0.7% after giving effect to the issuance of $2.0 million in outstanding but undrawn irrevocable standby letters of credit. As of December 31, 2021, the Partnership was in compliance with the Permian Transmission Credit Facilities covenants. There were no defaults or events of default during the period from the Permian Closing Date to December 31, 2021. 2026 Secured Notes. In 2021, the Co-Issuers issued $700.0 million of 8.500% Senior Secured Second Lien Notes due 2026 (the “2026 Secured Notes”) to eligible purchasers pursuant to Rule 144A and Regulation S of the Securities Act, at a price of 98.5% of their face value. The 2026 Secured Notes will pay interest semi-annually on April 15 and October 15 of each year, commencing on April 15, 2022, and will be jointly and severally guaranteed, on a senior second-priority secured basis (subject to permitted liens), by the Partnership and each restricted subsidiary of the Partnership (other than the Co-Issuers) that is an obligor under the ABL Agreement (as defined below), or under the Co-Issuers’ 2025 Senior Notes on the issue date of the 2026 Secured Notes. The 2026 Secured Notes will mature on October 15, 2026; provided that, if the outstanding amount of the 2025 Senior Notes (or any refinancing indebtedness in respect thereof that has a final maturity on or prior to the date that is 91 days after the Initial Maturity Date (as defined in the 2026 Secured Notes Indenture)) is greater than or equal to $50.0 million on January 14, 2025, which is 91 days prior to the scheduled maturity date of the 2025 Senior Notes, then the 2026 Secured Notes will mature on January 14, 2025. The Partnership used the net proceeds from the offering of the 2026 Secured Notes, together with cash on hand and borrowings under the ABL Facility (as defined below), to repay in full all of Summit Holdings’ obligations under the Revolving Credit Facility. 2026 Secured Notes Indenture. The Co-Issuers issued the 2026 Secured Notes pursuant to an indenture (the “2026 Secured Notes Indenture”), dated as of November 2, 2021, by and among the Co-Issuers, the Partnership, any other Restricted Subsidiary (as defined in the 2026 Secured Notes Indenture) of the Partnership that provides a Notes Guarantee (as defined in the 2026 Secured Notes Indenture) and Regions Bank, as trustee (the “Trustee”) and collateral agent, setting forth specific terms applicable to the 2026 Secured Notes. At any time prior to October 15, 2023, the Co-Issuers may on any one or more occasions redeem up to 35% of the aggregate principal amount of the 2026 Secured Notes (including any additional notes) issued under the 2026 Secured Notes Indenture at a redemption price of 108.5% of the principal amount of the 2026 Secured Notes, plus accrued and unpaid interest, if any, to, but not including, the redemption date, in an amount not greater than the net cash proceeds of certain equity offerings by the Partnership, provided that: (i) at least 65% of the initial aggregate principal amount of the 2026 Secured Notes (including any additional notes) remains outstanding immediately after the occurrence of such redemption (excluding notes held by the Partnership and its subsidiaries); and (ii) the redemption occurs within 180 days of the date of the closing of each such equity offering by the Partnership. On and after October 15, 2023, the Co-Issuers may redeem all or part of the 2026 Secured Notes at redemption prices (expressed as percentages of principal amount) equal to: (a) 104.250% for the twelve-month period beginning October 15, 2023; (b) 102.125% for the twelve-month period beginning October 15, 2024; and (c) 100.000% for the twelve-month period beginning on October 15, 2025 and at any time thereafter, in each case plus accrued and unpaid interest, if any, to, but not including, the redemption date. In certain circumstances, the Co-Issuers will be required to offer to purchase the 2026 Secured Notes with excess proceeds from asset sales, excess cash flow and upon the occurrence of certain change of control events. The 2026 Secured Notes Indenture restricts the Partnership’s and its Restricted Subsidiaries’ ability and the ability of certain of their subsidiaries to: (i) incur additional debt or issue preferred stock; (ii) make distributions, repurchase equity or redeem junior lien, unsecured or subordinated debt; (iii) make payments on junior lien, unsecured or subordinated indebtedness; (iv) create liens or other encumbrances; (v) make investments, loans or other guarantees; (vi) engage in transactions with affiliates; and (viii) make acquisitions or merge or consolidate with another entity. These covenants are subject both to a number of important exceptions and qualifications. At any time when the 2026 Secured Notes are rated investment grade by at least two of Moody’s Investors Service, Inc., Standard & Poor’s Ratings Services or Fitch Ratings, Inc., no default under the 2026 Secured Notes Indenture has occurred and is continuing, many of these covenants will terminate. The 2026 Secured Notes Indenture contains certain events of default customary for instruments of this type. In the case of an event of default arising from certain events of bankruptcy, insolvency or reorganization with respect to either Co-Issuer, the Partnership, and certain significant subsidiaries of the Partnership, all outstanding Notes will become due and payable immediately without further action or notice. If any other event of default occurs and is continuing, the Trustee or the holders of at least 25% in principal amount of the then outstanding Notes may declare all the 2026 Secured Notes to be due and payable immediately. Collateral Agreement. On November 2, 2021, the Co-Issuers, as pledgors and grantors, entered into, in connection with the 2026 Secured Notes Indenture, a Collateral Agreement (Second Lien), with the Partnership, as a pledgor, each subsidiary guarantor listed therein and Regions Bank, as collateral agent (the “Collateral Agreement”). Pursuant to the Collateral Agreement and the 2026 Secured Notes Indenture, the obligations under the 2026 Secured Notes Indenture are (or, subject to post-closing periods for certain types of collateral, will be) generally secured by a second priority lien on and security interest in (subject to permitted liens) the assets of the Partnership, the Co-Issuers and the subsidiary guarantors securing their obligations under the ABL Facility (as described below under “—ABL Facility”). Excess Cash Flow Offers to Purchase. Starting in the first quarter of 2023 with respect to the fiscal year ended 2022, and continuing annually through the fiscal year 2025, the Partnership is required under the terms of the 2026 Secured Notes Indenture to, if it has Excess Cash Flow (as defined in the 2026 Secured Notes Indenture), and subject to its ability to make such an offer under the ABL Credit Facility, offer to purchase an amount of the 2026 Secured Notes, at 100% of the principal amount plus accrued and unpaid interest, equal to 100% of the Excess Cash Flow generated in the prior year. Generally, if the Partnership does not offer to purchase designated annual amounts of its 2026 Secured Notes or reduce its first lien capacity under the 2026 Secured Notes Indenture per annum from 2023 through 2025, the interest rate on the 2026 Secured Notes are subject to certain rate escalations. Per the terms of the 2026 Secured Notes Indenture, the designated amounts are $50.0 million in aggregate by April 1, 2023, otherwise the interest rate shall automatically increase by 50 basis points per annum; $100.0 million in aggregate by April 1, 2024, otherwise the interest rate shall automatically increase by 100 basis points per annum (minus any amount previously increased); and $200.0 million in aggregate by April 1, 2025, otherwise the interest rate shall automatically increase by 200 basis points per annum (minus any amount previously increased). To the extent the Partnership makes an offer to purchase, and the offer is not fully accepted by the holders of the 2026 Secured Notes, the Partnership may use any remaining amount not accepted for any purpose not prohibited by the 2026 Secured Notes Indenture or the ABL Facility. 2022 Senior Notes. In July 2014, the Co-Issuers co-issued the 2022 Senior Notes. During 2021, the Co-Issuers redeemed all of the outstanding 2022 Senior Notes at a redemption price equal to 100.0% of the principal amount of the 2022 Senior Notes, plus accrued and unpaid interest. 2025 Senior Notes. In February 2017, the Co-Issuers co-issued the 2025 Senior Notes. The Partnership pays interest on the 2025 Senior Notes semi-annually in cash in arrears on April 15 and October 15 of each year. The 2025 Senior Notes are senior, unsecured obligations and rank equally in right of payment with all of the Partnership’s existing and future senior obligations. The 2025 Senior Notes are effectively subordinated in right of payment to all of the Partnership’s secured indebtedness, to the extent of the collateral securing such indebtedness. The Co-Issuers have the right to redeem all or part of the 2025 Senior Notes at a redemption price of 102.875% (with the redemption price declining ratably each year to 100.00% on April 15, 2023), plus accrued and unpaid interest, if any, to, but not including, the redemption date. Debt issuance costs of $7.7 million are being amortized over the life of the 2025 Senior Notes. As of and during the year ended December 31, 2021, that Partnership was in compliance with the financial covenants governing its 2025 Senior Notes. SMPH Term Loan and TL Restructuring. Until November 17, 2020, a subsidiary of the Partnership, SMP Holdings, had a senior secured term loan facility with $155.2 million of principal outstanding and a maturity date of May 15, 2022. Borrowings under the SMPH Term Loan bore interest at LIBOR plus 6.00% or ABR plus 5.00%, as defined in the SMPH Term Loan, and were 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) 2.3 million SMLP 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. On September 29, 2020, SMP Holdings, Summit Investments and, for limited purposes, the Partnership, entered into the TL Restructuring. At the closing of the TL Restructuring on November 17, 2020, the Term Loan Agent executed a Strict Foreclosure on behalf of the Term Loan Lenders on the 2,306,972 common units held by SMP Holdings and pledged as collateral under the SMPH Term Loan, which was then distributed to all SMPH Term Loan Lenders on a pro rata basis. In addition to the Strict Foreclosure, SMP Holdings paid to each of the SMPH Term Loan Lenders its pro rata share of $26.5 million in cash that the Partnership paid to SMP Holdings to fully satisfy its obligation with respect to the deferred purchased price obligation. As of December 31, 2020, the SMPH Term Loan is fully satisfied and no longer exists. ECP 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) (“Mizuho”), as collateral agent, 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 were set to mature on March 31, 2021 and bore interest at a fixed rate of 8.00% per annum, with the interest payment due at maturity of the ECP Loans. With borrowings under the Partnership’s Revolving Credit Facility, the Partnership fully repaid all amounts outstanding under the ECP Loans ($35 million of principal and $0.6 million of accrued interest) on August 7, 2020.

LIABILITY MANAGEMENT TRANSACTIO

LIABILITY MANAGEMENT TRANSACTIONS	12 Months Ended
	Dec. 31, 2021
Liability Management Transactions [Abstract]
Liability Management Transactions	9. LIABILITY MANAGEMENT TRANSACTIONS During the year ended December 31, 2020, the Partnership and its subsidiaries completed several liability management transactions, described below, that resulted in the early extinguishment of an aggregate $306.5 million face value of the Partnership’s indebtedness. Open Market Repurchases. During the year ended December 31, 2020, the Partnership made a number of open market repurchases of the 2022 Senior Notes and 2025 Senior Notes that resulted in the extinguishment of $32.4 million of face value of the 2022 Senior Notes and $201.8 million of face value of the 2025 Senior Notes (the “Open Market Repurchases”). Total cash consideration paid to repurchase the principal amounts outstanding of the 2022 Senior Notes and 2025 Senior Notes, plus accrued interest totaled $150.3 million and the Partnership recognized a $86.4 million gain on the early extinguishment of debt during the year ended December 31, 2020. Debt Tender Offers. In September 2020, the Co-Issuers completed the Debt Tender Offers to purchase a portion of the 2022 Senior Notes and 2025 Senior Notes. Upon concluding the Debt Tender Offers, the Co-Issuers repurchased $33.5 million principal amount of the 2022 Senior Notes and $38.7 million principal amount of the 2025 Senior Notes. Total cash consideration paid to repurchase the principal amounts outstanding of the 2022 and 2025 Senior Notes, plus accrued interest, totaled $48.7 million, and the Partnership recognized a $23.3 million gain on the early extinguishment of debt during the year ended December 31, 2020. SMPH Term Loan Restructuring . On November 17, 2020, the Partnership completed the TL Restructuring and recognized a gain of $94.0 million equal to the difference between the face value of the cancelled SMPH Term Loan and the fair value of the total consideration transferred, including unamortized debt issuance costs, and certain direct transaction costs related to the restructuring. The transaction was accounted for under ASC Topic 470-60 “Troubled Debt Restructuring with Debtors” and had a total impact of $26.15 per unit. Summary of gain on extinguishment of debt. The Partnership recognized a $203.1 million gain on extinguishment of debt during the year ended December 31, 2020, the components of which are summarized in the table below. ECP Loan Open Market Tender TL Total 2022 2025 2022 2025 (in thousands) Senior Notes Senior Notes Senior Notes Senior Notes Gain on Repurchases of Senior Notes and TL Restructuring $ — $ 11,554 $ 76,789 $ 9,223 $ 15,479 $ 99,175 $ 212,220 Debt issue costs (361) (143) (1,541) (125) (351) (2,724) (5,245) Transaction costs (249) (105) (105) (467) (467) (2,520) (3,913) Gain (loss) on debt extinguishment $ (610) $ 11,306 $ 75,143 $ 8,631 $ 14,661 $ 93,931 $ 203,062

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	10. COMMITMENTS AND CONTINGENCIES Environmental Matters. Although the Partnership believes that it is in material compliance with applicable environmental regulations, the risk of environmental remediation costs and liabilities are inherent in pipeline ownership and operation. Furthermore, the Partnership can provide no assurances that significant environmental remediation costs and liabilities will not be incurred in the future. The Partnership is currently not aware of any material contingent liabilities that exist with respect to environmental matters, except as noted below. In 2015, the Partnership learned of the rupture of a four-inch produced water gathering pipeline on the Meadowlark Midstream system near Williston, North Dakota (“2015 Blacktail Release”). As of December 31, 2021, the Partnership has 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 expected to be incurred subsequent to December 31, 2022. Each of these amounts represent the Partnership’s best estimate for costs expected to be incurred. Neither of these amounts have been discounted to its present value. A rollforward of the Partnership’s undiscounted accrued environmental remediation follows and is primarily related to the 2015 Blacktail Release and other environmental remediation activities is below. (In thousands) Accrued environmental remediation, January 1, 2020 $ 4,651 Payments made (1,722) Accrued environmental remediation, December 31, 2020 $ 2,929 Payments made (1,972) Additional accruals 4,649 Accrued environmental remediation, December 31, 2021 $ 5,606 In the fourth quarter of 2020, the Partnership recognized a $17.0 million loss contingency for the 2015 Blacktail Release as a result of ongoing discussions with multiple federal and state government agencies, including the U.S. Department of Justice, the U.S. Environmental Protection Agency, the North Dakota Industrial Commission, the North Dakota Office of the Attorney General, the North Dakota Department of Environmental Quality, and the North Dakota Game and Fish Department. Subsequently, on August 4, 2021, the Partnership and several of its subsidiaries entered into the following agreements to resolve the U.S. federal and North Dakota state governments’ environmental claims with respect to the 2015 Blacktail Release: (i) a Consent Decree with (a) the U.S. Department of Justice (“DOJ”), on behalf of the U.S. Environmental Protection Agency and the U.S. Department of Interior, and (b) the State of North Dakota, on behalf of the North Dakota Department of Environmental Quality and the North Dakota Game and Fish Department (“Consent Decree”), lodged with the U.S. District Court for the District of North Dakota (“U.S. District Court”); (ii) a Plea Agreement with the United States, by and through the U.S. Attorney for the District of North Dakota, and the Environmental Crimes Section of the DOJ (“Plea Agreement”); and (iii) a Consent Agreement with the North Dakota Industrial Commission (“Consent Agreement” together with the Consent Decree and Plea Agreement, the “Global Settlement”). The Partnership increased its loss contingency for the 2015 Blacktail Release during the three months ended June 30, 2021 by $19.3 million. As of December 31, 2021, the accrued loss liability for the 2015 Blacktail Release was $33.2 million. Key terms of the Global Settlement include (i) payment of penalties and fines totaling $36.3 million, consisting of $1.25 million in natural resource damages to the federal and state governments payable after court approval of the Global Settlement, $25.0 million payable to the federal government over five years, and $10.0 million payable to the state governments over six years, with interest applied to unpaid amounts accruing at a fixed rate of 3.25%, and of which $5.6 million is expected to be paid within the next twelve months; (ii) continuation of remediation efforts at the site of the 2015 Blacktail Release; (iii) other injunctive relief including but not limited to control room management, environmental management system audit, training, and reporting; (iv) guilty pleas for one charge of negligent discharge of a harmful quantity of oil and one charge of knowing failure to immediately report a discharge of oil; and (v) organizational probation for a minimum period of three years from sentencing, including payment in full of certain components of the fines and penalty amounts. The agreements comprising the Global Settlement are subject to the approval of the U.S. District Court for the District of North Dakota (the “U.S. District Court”). The U.S. District Court entered an order making the civil components of the Global Settlement effective on September 28, 2021 and has set a hearing for December 6, 2021 on the criminal components of the Global Settlement, which if accepted by the U.S. District Court will complete approval of the Global Settlement. 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.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
FINANCIAL INSTRUMENTS	11. FINANCIAL INSTRUMENTS Concentrations of Credit Risk. Financial instruments that potentially subject the Partnership to concentrations of credit risk consist of cash and cash equivalents, restricted cash and accounts receivable. The Partnership maintains its cash and cash equivalents and restricted cash in bank deposit accounts that frequently exceed federally insured limits. The Partnership has not experienced any losses in such accounts and does not believe it is exposed to any significant risk. Accounts receivable primarily comprise amounts due for the gathering, compression, treating and processing services the Partnership provides to its customers and also the sale of natural gas liquids resulting from its processing services. This industry concentration has the potential to impact its overall exposure to credit risk, either positively or negatively, in that the Partnerships customers may be similarly affected by changes in economic, industry or other conditions. The Partnership monitors the creditworthiness of its 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. The Partnership’s top five customers or counterparties accounted for 38% of its total accounts receivable at December 31, 2021, compared to 51% as of December 31, 2020. Fair Value. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable and trade accounts payable reported on the consolidated balance sheet approximates fair value due to their short-term maturities. A summary of the estimated fair value of the Partnerships debt financial instruments follows. December 31, 2021 December 31, 2020 Carrying Value (1) Estimated Carrying Value (1) Estimated (in thousands) 2022 Senior Notes $ — $ — $ 234,047 $ 215,713 2025 Senior Notes 259,463 234,814 259,463 168,002 2026 Secured Notes 700,000 718,083 — — (1) Excludes applicable unamortized debt issuance costs and debt discounts. The carrying value on the balance sheets of the ABL Facility, Revolving Credit Facility and Permian Transmission Credit Facility is its fair value due to its floating interest rate. The fair value for the 2026 Secured Notes, 2022 Senior Notes and 2025 Senior Notes is based on an average of nonbinding broker quotes as of December 31, 2021 and 2020. The use of different market assumptions or valuation methodologies may have a material effect on the estimated fair value of the Senior Notes. Interest Rate Swaps. In connection with the Permian Transmission Credit Facility, the Partnership entered into amortizing interest rate swap agreements for a notional amount of $144.0 million. These interest rate swaps manage exposure to variability in expected cash flows attributable to interest rate risk. Interest rate swaps convert a portion of the Partnership’s variable rate debt to fixed rate debt. The Partnership chooses counterparties for its derivative instruments that it believes are creditworthy at the time the transactions are entered into, and the Partnership actively monitors the creditworthiness where applicable. However, there can be no assurance that a counterparty will be able to meet its obligations to the Partnership. The Partnership presents its derivative positions on a gross basis and does not net the asset and liability positions. As of December 31, 2021, the Partnership’s interest rate swap agreements had a fair value of $0.8 million and are recorded within other current liabilities and other noncurrent liabilities within the consolidated balance sheets.

PARTNERS' CAPITAL AND MEZZANINE

PARTNERS' CAPITAL AND MEZZANINE CAPITAL	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
PARTNERS' CAPITAL AND MEZZANINE CAPITAL	12. PARTNERS' CAPITAL AND MEZZANINE CAPITAL Common Units. A rollforward of the number of common limited partner units follows for the period from December 31, 2019 to December 31, 2021. Common Units (2) December 31, 2019 3,021,258 GP Buy-In Transaction (1) (132,687) Common units issued for SMLP LTIP, net 95,987 TL Restructuring 2,306,972 Series A Preferred Unit Exchange Offer, net of units withheld for taxes 817,845 Other 717 December 31, 2020 6,110,092 2021 Preferred Exchange Offer, net of units withheld for taxes 538,715 Common units issued for SMLP LTIP, net 106,580 ECP Warrant Exercise 414,447 December 31, 2021 7,169,834 (1) The purchase price for the SMLP common units reflected in the consolidated statement of partners’ capital for the year ended December 31, 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 0.7 million warrants, and (iii) $6.8 million of advisory fees and other direct costs related to closing the GP Buy-In Transaction. (2) As adjusted for reverse unit split. Series A Preferred Units. In November 2017, the Partnership issued 300,000 Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series A Preferred Units”) representing limited partner interests in the Partnership at a price to the public of $1,000 per unit. The Series A Preferred Units rank senior to (i) common units representing limited partner interests in the Partnership and (ii) each other class or series of limited partner interests or other equity securities in the Partnership that may be established in the future that expressly ranks junior to the Series A Preferred Units as to the payment of distributions and amounts payable upon a liquidation event. The Series A Preferred Units rank equal in all respects with each class or series of limited partner interests or other equity securities in the Partnership that may be established in the future that is not expressly made senior or subordinated to the Series A Preferred Units as to the payment of distributions and amounts payable on a liquidation event. The Series A Preferred Units rank junior to (i) all of the Partnership’s existing and future indebtedness and other liabilities with respect to assets available to satisfy claims against the Partnership and (ii) each other class or series of limited partner interests or other equity securities in the Partnership established in the future that is expressly made senior to the Series A Preferred Units as to the payment of distributions and amounts payable upon a liquidation event. Income is allocated to the Series A Preferred Units in an amount equal to the earned distributions (whether these distributions are declared by the General Partner to be paid or not) for the respective reporting period. Distributions on the Series A Preferred Units are cumulative and compounding and are payable semi-annually in arrears on the 15th day of each June and December through and including December 15, 2022, and, thereafter, quarterly in arrears on the 15th day of March, June, September and December of each year (each, a “Distribution Payment Date”) to holders of record as of the close of business on the first business day of the month of the applicable Distribution Payment Date, in each case, when, as, and if declared by the General Partner out of legally available funds for such purpose. The initial distribution rate for the Series A Preferred Units is 9.50% per annum of the $1,000 liquidation preference per Series A Preferred Unit. On and after December 15, 2022, distributions on the Series A Preferred Units will accumulate for each distribution period at a percentage of the liquidation preference equal to the three-month LIBOR plus a spread of 7.43%. In connection with the GP Buy-In Transaction, the Partnership suspended its distributions to be paid to holders of its Series A Preferred Units, commencing with respect to the quarter ending March 31, 2020. As of December 31, 2021, the amount of accrued and unpaid distributions on the Series A Preferred Units was $29.9 million. A rollforward of the number of Series A Preferred Units follows for the period from December 31, 2019 to December 31, 2021. Series A December 31, 2019 300,000 Series A Preferred Unit Exchange Offer (62,816) Series A Preferred Unit Tender (75,075) December 31, 2020 162,109 Series A Preferred Unit Exchange Offer (18,662) December 31, 2021 143,447 Series A Preferred Unit Exchange Offers . In April 2021, the Partnership completed an offer to exchange its Series A Preferred Units for newly issued common units, whereby it issued 538,715 SMLP common units, net of units withheld for withholding taxes, in exchange for 18,662 Series A Preferred Units. In July 2020, the Partnership completed an offer to exchange its Series A Preferred Units for newly issued common units, whereby it issued 817,845 SMLP common units, net of units withheld for withholding taxes, in exchange for 62,816 Series A Preferred Units. Series A Preferred Tender Offer. In December 2020, the Partnership completed a cash tender offer for its Series A Preferred Units whereby it accepted 75,075 Series A Preferred Units for a purchase price of $333.00 per Series A Preferred Unit and an aggregate purchase price of $25.0 million. Subsidiary Series A Preferred Units. The Partnership has Subsidiary Series A Preferred Units that ranks senior to each other class or series of limited partner interests or other equity securities in Permian Holdco that may be established in the future that expressly ranks junior to the Subsidiary Series A Preferred Units as to the payment of distributions and amounts payable upon a liquidation event. The Subsidiary Series A Preferred Units rank equal in all respects with each class or series of limited partner interests or other equity securities in Permian Holdco that may be established in the future that is not expressly made senior or subordinated to the Subsidiary Series A Preferred Units as to the payment of distributions and amounts payable on a liquidation event. The Subsidiary Series A Preferred Units rank junior to (i) all of Permian Holdco’s or a subsidiary of Permian Holdco’s future indebtedness and other liabilities with respect to assets available to satisfy claims against Permian Holdco and (ii) each other class or series of limited partner interests or other equity securities in Permian Holdco established in the future that is expressly made senior to the Subsidiary Series A Preferred Units as to the payment of distributions and amounts payable upon a liquidation event. Income is allocated to the Subsidiary Series A Preferred Units in an amount equal to the earned distributions for the respective reporting period. Distributions on the Subsidiary Series A Preferred Units are cumulative and compounding and are payable 21 days following the quarterly period ended March, June, September and December of each year (each, a “Series A Distribution Payment Date”) to holders of record as of the close of business on the first business day of the month of the applicable Series A Distribution Payment Date, in each case, when, as, and if declared by Permian Holdco out of legally available funds for such purpose. The distribution rate for the Subsidiary Series A Preferred Units is 7.00% per annum of the $1,000 liquidation preference per Subsidiary Series A Preferred Unit. A pro-rated initial distribution on the Subsidiary Series A Preferred Units was Paid-in-kind (“PIK”) on January 21, 2020 in an amount equal to 7.00% per Subsidiary Series A Preferred Unit plus 1.00% per annum of the undrawn commitment units. In 2020, the Partnership issued 50,000 Subsidiary Series A Preferred Units at a price of $1,000 per unit for net proceeds of $48.7 million (after deducting underwriting discounts and offering expenses). All proceeds were used to fund capital expenses associated with the Double E Project. These Subsidiary Series A Preferred Units are considered redeemable securities under GAAP due to the existence of certain redemption provisions that are outside of the Partnership’s control. Therefore, the securities are classified as temporary equity in the mezzanine section of the consolidated balance sheets. The Partnership records its Subsidiary Series A Preferred Units at fair value upon issuance, net of issuance costs, and subsequently records an effective interest method accretion amount each reporting period to accrete the carrying value to a most probable redemption value that is based on a predetermined internal rate of return measure. The Partnership also elected to make PIK distributions to holders of the Subsidiary Series A Preferred Units during the years ended December 31, 2021 and 2020, which increase the liquidation preference on each Subsidiary Series A Preferred Unit. Ultimately, Net Income (Loss) Attributable to common limited partners includes adjustments for PIK distributions and redemption accretion. During the years ended December 31, 2021 and 2020, the Partnership issued 6,131 and 5,251 Subsidiary Series A Preferred Units, respectively, through PIK transactions. As of December 31, 2021 and 2020, the Partnership had 91,439 and 85,308 Subsidiary Series A Preferred Units outstanding, respectively. If the Subsidiary Series A Preferred Units were redeemed on December 31, 2021, the redemption amount would be $114.3 million, when considering the applicable multiple of invested capital metric and make-whole amount provisions contained in the Subsidiary Series A Preferred Unit agreement. The following table shows the change in the Partnership’s Subsidiary Series A Preferred Unit balance during the year ended December 31, 2021: (in thousands) Balance at January 1, 2020 $ 27,450 New issuances 50,000 PIK distributions 5,251 Issuance costs (1,290) Redemption accretion 8,247 Balance at December 31, 2020 $ 89,658 PIK distributions 6,131 Redemption accretion 10,536 Balance at December 31, 2021 (1) $ 106,325 (1) Amount is net of $3.9 million of issuance costs at December 31, 2021. Warrants. On May 28, 2020 and in connection with the GP Buy-In Transaction, the Partnership issued (i) a warrant to purchase up to 537,307 SMLP common units (8,059,609 SMLP common units prior to the Reverse Unit Split) to ECP NewCo (the “ECP NewCo Warrant”) and (ii) a warrant to purchase up to 129,360 SMLP common units (1,940,391 SMLP common units prior to the Reverse Unit Split) to ECP Holdings (the “ECP Holdings Warrant” and together with the ECP NewCo Warrant, the “ECP Warrants”). The exercise price under the ECP Warrants was 15.35 per SMLP common unit. At issuance the ECP Warrants were valued at $2.3 million using a Black-Scholes model and accounted for as a liability instrument. On August 5, 2021, the ECP Entities cashlessly exercised all of the ECP Warrants for an aggregate of 414,447 SMLP common units, net of the exercise price, as calculated pursuant to Section 3(c) of the ECP Warrants (the "ECP Warrant Exercise"). For the year ended December 31, 2021, the Partnership recognized a $13.6 million loss related to the ECP Warrants. Cash Distribution Policy. In connection with the GP Buy-In Transaction, the Partnership suspended its cash distributions to holders of its common units, commencing with respect to the quarter ending March 31, 2020. Upon the resumption of distributions, the Partnership Agreement requires that it distribute all available cash, subject to reserves established by its General Partner, within 45 days after the end of each quarter to unitholders of record on the applicable record date. The amount of distributions paid under this policy is subject to fluctuations based on the amount of cash the Partnership generates from its business and the decision to make any distribution is determined by the General Partner, taking into consideration the terms of the Partnership Agreement. Cash Distributions Paid and Declared. Prior to the GP Buy-In Transaction, on January 29, 2020, the Board of Directors declared a distribution of $0.125 per unit for the quarterly period ended December 31, 2020 This distribution, which totaled $11.7 million, was paid on February 14, 2020 to unitholders of record at the close of business on February 7, 2020.

EARNINGS PER UNIT

EARNINGS PER UNIT	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
EARNINGS PER UNIT	13. EARNINGS PER UNIT The following table details the components of EPU. Year ended December 31, 2021 2020 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net income (loss) among limited partner interests: Net income (loss) $ (19,949) $ 189,078 Net income attributable to Subsidiary Series A Preferred Units (16,667) (13,498) Net loss attributable to noncontrolling interest — 3,274 Net income (loss) attributable Summit Midstream Partners, LP (36,616) 178,854 Less: Net income attributable to Series A Preferred Unit (15,998) (26,529) Add: Deemed capital contribution 8,326 110,669 Net income (loss) attributable to common limited partners $ (44,288) $ 262,994 Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic 6,741 3,592 Effect of nonvested phantom units — 102 Weighted-average common units outstanding – diluted 6,741 3,694 Net Income (Loss) per limited partner unit: Common unit – basic $ (6.57) $ 73.22 Common unit – diluted $ (6.57) $ 71.19 Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 203 240

UNIT-BASED AND NONCASH COMPENSA

UNIT-BASED AND NONCASH COMPENSATION	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
UNIT-BASED AND NONCASH COMPENSATION	15. UNIT-BASED AND NONCASH COMPENSATION SMLP Long-Term Incentive Plan. The Partnership’s Long-Term Incentive Plan (“SMLP LTIP”) provides for equity awards to eligible officers, employees, consultants and directors of the Partnership, thereby linking the recipients' compensation directly to SMLP’s performance. The SMLP LTIP provides for the granting, from time to time, of unit-based awards, including common units, restricted units, phantom units, unit options, unit appreciation rights, distribution equivalent rights, profits interest units and other unit-based awards. Grants are made at the discretion of the Board of Directors or Compensation Committee. A total of 1.0 million common units was reserved for issuance pursuant to and in accordance with the SMLP LTIP. As of December 31, 2021, approximately 0.3 million common units remained available for future issuance. Significant items for the year ended December 31, 2021: • For the year ended December 31, 2021, the Partnership granted 159,239 phantom units and associated distribution equivalent rights to employees. These awards had a grant date fair value of $20.65 per common unit and vest ratably over a three-year period. • For the year ended December 31, 2021, the Partnership issued 40,002 common units to the Partnership’s six independent directors in connection with their annual compensation plan. These awards had a grant date fair value of $28.99 per common unit and vested immediately. The following table presents phantom unit activity for the periods presented: Units Weighted-average grant date fair value Nonvested phantom units, December 31, 2019 140,400 $ 115.35 Phantom units granted 345,997 9.20 Phantom units vested (193,349) 54.07 Phantom units forfeited (1,357) 119.24 Nonvested phantom units, December 31, 2020 291,691 26.57 Phantom units granted 199,241 22.33 Phantom units vested (143,768) 30.66 Phantom units forfeited (13,385) 38.85 Nonvested phantom units, December 31, 2021 333,779 $ 21.78 A phantom unit is a notional unit that entitles the grantee to receive a common unit upon the vesting of the phantom unit or on a deferred basis upon specified future dates or events or, in the discretion of the administrator, cash equal to the fair market value of a common unit. Distribution equivalent rights for each phantom unit provide for a lump sum cash amount equal to the accrued distributions from the grant date to be paid in cash upon the vesting date. P hantom units granted to date generally vest ratably over a three Forfeitures are recorded as incurred. Holders of all phantom units granted to date are entitled to receive distribution equivalent rights for each phantom unit, providing for a lump sum cash amount equal to the accrued distributions from the grant date of the phantom units to be paid in cash upon the vesting date. Upon vesting, phantom unit awards may be settled, at the Partnership’s discretion, in cash and/or common units, but the current intention is to settle all phantom unit awards with common units. The intrinsic value of phantom units that vested during the years ended December 31, follows. Year ended December 31, 2021 2020 (In thousands) Intrinsic value of vested LTIP awards $ 4,407 $ 2,602 As of December 31, 2021, the unrecognized unit-based compensation related to the SMLP LTIP was $2.6 million. Incremental unit-based compensation will be recorded over the remaining weighted-average vesting period of approximately 1.3 years. Unit-based compensation recognized in general and administrative expense related to awards under the SMLP LTIP follows. Year ended December 31, 2021 2020 (In thousands) SMLP LTIP unit-based compensation $ 4,744 $ 8,111

LEASES

LEASES	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
LEASES	16. LEASES Leases. The Partnership leases certain office space and equipment under operating leases. The Partnership leases office space for terms of between 3 and 10 years. Office space leases limit exposure to risks related to ownership, such as fluctuations in real estate prices. The Partnership leases equipment primarily to support its operations in response to the needs of its gathering systems for terms of between 3 and 4 years. The Partnership also leases vehicles under finance leases to support its operations in response to the needs of its gathering systems for a term of 3 years. Some of the Partnerships leases are subject to annual escalations relating to the Consumer Price Index (“CPI”). While lease liabilities are not remeasured as a result of changes to the CPI, changes to the CPI are treated as variable lease payments and recognized in the period in which the obligation for those payments was incurred. Significant assumptions or judgments include the determination of whether a contract contains a lease and the discount rate used in the lease liabilities. The rate implicit in the lease contracts are not readily determinable. In determining the discount rate used in for lease liabilities, the Partnership analyzed certain factors in its incremental borrowing rate, including collateral assumptions and the term used. The incremental borrowing rate on the ABL Facility was 3.38% at December 31, 2021, which reflects the fixed rate at which the Partnership could borrow a similar amount, for a similar term and with similar collateral as in the lease contracts at the commencement date. ROU assets (included in the other noncurrent assets Other current liabilities Other noncurrent liabilities December 31, 2021 December 31, 2020 (In thousands) ROU assets Operating $ 2,515 $ 3,736 Finance 792 1,748 $ 3,307 $ 5,484 Lease liabilities, current Operating $ 1,213 $ 2,298 Finance 167 618 $ 1,380 $ 2,916 Lease liabilities, noncurrent Operating $ 2,272 $ 3,182 Finance 122 154 $ 2,394 $ 3,336 Lease cost and Other information follow: Year ended December 31, 2021 2020 (In thousands) Lease cost Finance lease cost: Amortization of ROU assets (included in depreciation and amortization) $ 1,026 $ 1,274 Interest on lease liabilities (included in interest expense) 20 52 Operating lease cost (included in general and administrative expense) 1,722 2,644 $ 2,768 $ 3,970 Year ended December 31, 2021 2020 (In thousands) Other information Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows from operating leases $ 1,407 $ 1,472 Operating cash outflows from finance leases 20 52 Financing cash outflows from finance leases 634 1,150 ROU assets obtained in exchange for new operating lease liabilities — 3,552 ROU assets obtained in exchange for new finance lease liabilities 94 133 Weighted-average remaining lease term (years) - operating leases 5.1 4.9 Weighted-average remaining lease term (years) - finance leases 1.1 1.4 Weighted-average discount rate - operating leases 5 % 5 % Weighted-average discount rate - finance leases 4 % 4 % The Partnership recognizes total lease expense incurred or allocated to us in general and administrative expenses. Lease expense related to operating leases, including lease expense incurred on the Partnership’s behalf and allocated to us, was as follows: Year ended December 31, 2021 2020 (In thousands) Lease expense $ 2,479 $ 3,436 Future minimum lease payments due under noncancelable leases at December 31, 2021, were as follows: December 31, 2021 (In thousands) Operating Finance 2022 $ 1,173 $ 173 2023 854 88 2024 573 38 2025 464 — 2026 156 — 2027 160 — Thereafter 418 — Total future minimum lease payments $ 3,798 $ 299

RESTRUCTURING

RESTRUCTURING	12 Months Ended
	Dec. 31, 2021
Restructuring and Related Activities [Abstract]
RESTRUCTURING	17. RESTRUCTURING 2020 Restructuring Activities. In late 2020, management initiated the 2020 Restructuring Plan, resulting in certain management, facility and organizational changes. Under the 2020 Restructuring Plan, and during the years ended December 31, 2021 and 2020, the Partnership expensed approximately $0.9 million and $5.6 million, respectively, of costs associated with these restructuring activities. These activities consisted primarily of employee-related severance costs and are included within the General and administrative caption on the consolidated statement of operations. 2019 Restructuring Activities. In 2019, management approved and initiated a plan to restructure its operations (“2019 Restructuring Plan”), resulting in certain management, facility and organizational changes. Under the 2019 Restructuring Plan, the Partnership expensed approximately $3.5 million, of costs associated with its restructuring activities. These activities consisted primarily of employee-related costs and consulting costs in support of the project. These costs are included within the General and administrative caption on the consolidated statement of operations . Details for the 2020 and 2019 Restructuring Plans follow. Severance Charges Other Restructuring Charges Total Severance and Other 2021 2020 2021 2020 2021 2020 (In thousands) 2020 Restructuring Plan $ 810 $ 5,591 $ 104 $ 56 $ 914 $ 5,647 2019 Restructuring Plan — 2,159 — 1,293 — 3,452 $ 810 $ 7,750 $ 104 $ 1,349 $ 914 $ 9,099 Accrued December 31, 2019 Charges Incurred Cash Payments Accrued December 31, 2020 Charges Incurred Cash Payments Accrued December 31, 2021 (In thousands) Employee-related costs $ 2,816 $ 7,750 $ (7,018) $ 3,548 $ 810 $ (4,358) $ — Other — 1,349 (1,349) — 104 (104) — Total restructuring costs $ 2,816 $ 9,099 $ (8,367) $ 3,548 $ 914 $ (4,462) $ —

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
SEGMENT INFORMATION	18. SEGMENT INFORMATION In accordance with ASC No. 280 - Segment Reporting, the Partnership routinely evaluates whether its reportable segments have changed. In the fourth quarter of 2021, the Partnership changed its segment reporting to align with how the General Partner’s Chief Executive Officer, its chief operating decision maker, reviews financial information in order to allocate resources and assess performance. The new segment reporting resulted from changes enacted to optimize commercial efforts and geographic workforce in order to better align its commercial, engineering, and operational capabilities. The Partnership’s current reportable segments are described below. • Rockies – Includes the Partnership’s wholly owned midstream assets located in the Williston Basin and the DJ Basin. • Permian – Includes the Partnership’s wholly owned midstream assets located in the Permian Basin and the equity method investment in Double E. • Northeast – Includes the Partnership’s wholly owned midstream assets located in the Utica and Marcellus shale plays and the equity method investment in Ohio Gathering that is focused on the Utica Shale. • Piceance – Includes the Partnership’s wholly owned midstream assets located in the Piceance Basin. • Barnett – Includes the Partnership’s wholly owned midstream assets located in the Barnett Shale. Corporate and Other represents those results that: (i) are not specifically attributable to a reportable segment; (ii) are not individually reportable; or (iii) have not been allocated to a reportable segments for the purpose of evaluating their performance, including certain general and administrative expense items, certain natural gas and crude oil marketing services and transaction costs. Assets by reportable segment follow. December 31, 2021 2020 (in thousands) Assets: Northeast $ 623,224 $ 645,754 Rockies 592,148 625,793 Permian 458,988 299,421 Piceance 524,218 579,800 Barnett 315,055 336,629 Total reportable segment assets 2,513,633 2,487,397 Corporate and Other 8,829 12,420 Total assets $ 2,522,462 $ 2,499,817 Revenues by reportable segment follow. Year ended December 31, 2021 2020 (In thousands) Revenues: Northeast $ 62,567 $ 62,250 Rockies 145,087 120,765 Permian 40,848 32,109 Piceance 105,485 113,890 Barnett 46,591 54,459 Total reportable segments revenue 400,578 383,473 Corporate and Other 40 — Total revenues $ 400,618 $ 383,473 Counterparties accounting for a significant portion of total revenues were as follows: Year ended December 31, 2021 2020 Percentage of total revenues (1) : Counterparty A - Piceance 12 % 13 % Counterparty B - Northeast * 5 % Counterparty B - Permian * 5 % Counterparty B - Barnett * 1 % ________________________________________________________ * Less than 10% in the aggregate Depreciation and amortization, including the amortization expense associated with the Partnership’s favorable and unfavorable gas gathering contracts as reported in other revenues, by reportable segment follows. Year ended December 31, 2021 2020 (In thousands) Depreciation and amortization: Northeast $ 17,054 $ 16,891 Rockies 29,513 32,057 Permian 5,858 5,455 Piceance 48,773 45,203 Barnett (1) 16,133 16,112 Total reportable segment depreciation and amortization 117,331 115,718 Corporate and Other 2,664 3,352 Total depreciation and amortization $ 119,995 $ 119,070 ______________________________________ (1) Includes the amortization expense associated with the Partnership’s favorable and unfavorable gas gathering contracts as reported in Other revenues. Cash paid for capital expenditures by reportable segment follow. Year ended December 31, 2021 2020 (In thousands) Cash paid for capital expenditures: Northeast $ 11,237 $ 7,657 Rockies 9,875 21,596 Permian 2,042 7,014 Piceance 579 1,370 Barnett 766 1,878 Total reportable segment capital expenditures 24,499 39,515 Corporate and Other 531 3,613 Total cash paid for capital expenditures $ 25,030 $ 43,128 The Partnership assesses the performance of its reportable segments based on segment adjusted EBITDA. The Partnership defines segment adjusted EBITDA as total revenues less total costs and expenses; plus (i) other income excluding interest income, (ii) 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 (vii) other noncash expenses or losses, less other noncash income or gains and (ix) restructuring expenses. Proportional adjusted EBITDA for the Partnership’s equity method investees is defined 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) ownership interest in Ohio Gathering during the respective period. For the purpose of evaluating segment performance, the Partnership excludes 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. Year ended December 31, 2021 2020 (In thousands) Reportable segment adjusted EBITDA Northeast $ 83,287 $ 85,854 Rockies 64,517 71,509 Permian 6,614 5,744 Piceance 76,131 88,820 Barnett 36,729 32,093 Total of reportable segments' measures of profit $ 267,278 $ 284,020 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. Year ended December 31, 2021 2020 (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 $ (28,156) $ 177,661 Add: Corporate and Other expense 68,783 60,903 Interest expense 66,156 78,894 Gain on early extinguishment of debt 3,523 (203,062) Depreciation and amortization (1) 119,995 119,070 Proportional adjusted EBITDA for equity method investees 29,022 31,056 Adjustments related to capital reimbursement activity (6,571) (1,395) Unit-based and noncash compensation 4,744 8,111 Gain on asset sales, net (369) (307) Long-lived asset impairment 10,151 13,089 Total of reportable segments' measures of profit $ 267,278 $ 284,020 ______________________________________ (1) Includes the amortization expense associated with the Partnership’s favorable gas gathering contracts as reported in other revenues. For the years ended December 31, 2021 and 2020, adjustments related to MVC shortfall payments recognize the earnings from MVC shortfall payments ratably over the term of the associated MVC. Contributions in aid of construction are recognized over the remaining term of the respective contract. The Partnership includes adjustments related to capital reimbursement activity in its calculation of segment adjusted EBITDA to account for revenue recognized from contributions in aid of construction.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	19. SUBSEQUENT EVENTS 2022 Preferred Exchange Offer. On January 12, 2022, the Partnership completed an offer to exchange its Series A Preferred Units and accepted for exchange 77,939 Series A Preferred Units for the issuance of 2,853,875 SMLP common units, net of units withheld for withholding taxes.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Presentation and Consolidation	The Partnership prepares its consolidated financial statements in accordance with GAAP as established by the FASB. The Partnership makes 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. Although management believes these estimates are reasonable, actual results could differ from its estimates.The consolidated financial statements include the assets, liabilities and results of operations of SMLP and its subsidiaries. All intercompany transactions among the consolidated entities have been eliminated in consolidation. Comprehensive income or loss is the same as net income or loss for all periods presented.
Cash, Cash Equivalents and Restricted Cash	The Partnership considers 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 the Partnership is classified as restricted cash. The restricted cash balance of $12.2 million at December 31, 2021 is related to proceeds which are available to finance Permian Transmission’s capital calls associated with its investment in Double E, for debt service or other general corporate purposes of Permiam Transmission. See Note 8 - Debt for additional information.
Accounts Receivable	Accounts receivable relate to gathering and other services provided to the Partnership’s customers and other counterparties. The Partnership evaluates the collectability of accounts receivable and the need for an allowance for doubtful accounts based on customer-specific facts and circumstances. To the extent the collectability of a specific customer or counterparty receivable is doubtful, the Partnership recognizes an allowance for doubtful accounts. Uncollectible receivables are written off when a settlement is reached for an amount that is less than the outstanding historical balance or a receivable amount is deemed otherwise unrealizable.
Property, Plant and Equipment	The Partnership records property, plant and equipment at historical cost of construction or fair value of the assets at acquisition. The Partnership capitalizes expenditures that extend the useful life of an asset or enhance its productivity or efficiency from its original design over the expected remaining period of use. For maintenance and repairs that do not add capacity or extend the useful life of an asset, the Partnership recognizes expenditures as an expense as incurred. The Partnership capitalizes project costs incurred during construction, including interest on funds borrowed to finance the construction of facilities, as construction in progress. Accrued capital expenditures are reflected in trade accounts payable. The Partnership records depreciation on a straight-line basis over an asset’s estimated useful life and bases its estimates for useful life on various factors including age (in the case of acquired assets), manufacturing specifications, technological advances and historical data concerning useful lives of similar assets. Estimates of useful lives follow. Useful lives (In years) Gathering and processing systems and related equipment 12-30 Other 4-15 Construction in progress is depreciated consistent with its applicable asset class once it is placed in service. Land and line fill are not depreciated. The Partnership bases an asset’s carrying value on estimates, assumptions and judgments for useful life and salvage value. Upon sale, retirement or other disposal, the Partnership removes the carrying value of an asset and its accumulated depreciation from its balance sheet and recognizes the related gain or loss, if any.
Asset Retirement Obligations	The Partnership records a liability for asset retirement obligations only if and when a future asset retirement obligation with a determinable life is identified. For identified asset retirement obligations, the Partnership evaluates whether the expected retirement date and related costs of retirement can be estimated. The Partnership has concluded that its gathering and processing assets have an indeterminate life because they are owned and will operate for an indeterminate period when properly maintained. Because the Partnership does not have sufficient information to reasonably estimate the amount or timing of such obligations and does not have any current plan to discontinue use of any significant assets, the Partnership did not provide for any asset retirement obligations as of December 31, 2021 or 2020.
Amortizing Intangibles	The Partnership has certain acquired gas gathering contracts that had above-market pricing structures at the acquisition date and the Partnership amortizes these favorable contracts using a straight-line method over the contract’s estimated useful life. The Partnership defines useful life as the period over which the contract is expected to contribute to the Partnership’s future cash flows. These favorable contracts have original terms ranging from 10 years to 20 years and the Partnership recognizes the amortization expense associated with these contracts in Other revenues. The Partnership amortizes all other gas gathering contracts, or contract intangibles, over the period of economic benefit based upon expected revenues over the life of the contract. The useful life of these contracts ranges from 3 years to 25 years. The Partnership recognizes the amortization expense associated with these contracts in Depreciation and amortization expense. The Partnership also has rights-of-way associated with municipal easements and easements granted within existing rights-of-way. The Partnership amortizes these intangible assets over the shorter of the contractual term of the rights-of-way or the estimated useful life of the gathering system. The contractual terms of the rights-of-way range from 20 years to 30 years and the Partnership recognizes the amortization expense associated with these rights-of-way assets in Depreciation and amortization expense.
Equity Method Investments	The Partnership accounts for investments in which it exercises significant influence using the equity method so long as it (i) does not control the investee and (ii) is not the primary beneficiary. The Partnership reflects these investments in its consolidated balance sheets under the caption titled “investment in equity method investees.”The Partnership recognizes an other-than-temporary impairment for losses in the value of equity method investees when evidence indicates that the carrying amount is no longer supportable. Evidence of a loss in value might include, but is not limited to, absence of an ability to recover the carrying amount of the investment or an inability of the equity method investee to sustain an earnings capacity that would justify the carrying amount of the investment. A current fair value of an investment that is less than its carrying amount may indicate a loss in value of the investment. The Partnership evaluates its equity method investments whenever a triggering event exists that would indicate a need to assess the investment for potential impairment.
Impairment of Long-Lived Assets	The Partnership tests assets for impairment when events or circumstances indicate the carrying value of a long-lived asset may not be recoverable. The carrying value of a long-lived asset (except goodwill) is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from its use and eventual disposition. If the Partnership concludes that an assets carrying value will not be recovered through future cash flows, the Partnership recognizes an impairment loss on the long-lived asset equal to the amount by which the carrying value exceeds its fair value. The Partnership determines fair value using a combination of market-based and income-based approaches.
Environmental Matters	The Partnership is subject to various federal, state and local laws and regulations relating to the protection of the environment. Liabilities for loss contingencies, including environmental remediation costs, arising from claims, assessments, litigation, fines and penalties and other sources are charged to expense when it is probable that a liability has been incurred and the amount of the assessment and/or remediation can be reasonably estimated. The Partnership accrues for losses associated with environmental remediation obligations when such losses are probable and reasonably estimable. Such accruals are adjusted as further information develops or circumstances change. Recoveries of environmental remediation costs from other parties or insurers are recorded as assets when their realization is assured beyond a reasonable doubt.
Commitments and Contingencies	When required, the Partnership records accruals for loss contingencies in accordance with FASB ASC 450, Contingencies . Such determinations are subject to interpretations of current facts and circumstances, forecasts of future events and estimates of the financial impacts of such events.
Noncontrolling Interest and Mezzanine Capital	A noncontrolling interest represents the portion of a consolidated subsidiary that is owned by a third party. Amounts are adjusted by the noncontrolling interest holder’s proportionate share of the subsidiary’s earnings or losses each period and any distributions that are paid. A noncontrolling interest is reported as a component of equity unless the noncontrolling interest is considered redeemable, in which case the noncontrolling interest is recorded between liabilities and equity (mezzanine or temporary equity) in the Partnership’s consolidated balance sheet.
Revenue Recognition	The Partnership provides gathering and/or processing services principally under contracts that contain one or more of the following arrangements described below: • Fee-based arrangements. Under fee-based arrangements, the Partnership receives a fee or fees for one or more of the following services (i) natural gas gathering, treating, transporting, compressing and/or processing and (ii) crude oil and/or produced water gathering. • Percent-of-proceeds arrangements. Under percent-of-proceeds arrangements, the Partnership generally purchases natural gas from producers at the wellhead, or other receipt points, gathers the wellhead natural gas through its gathering system, treats and compresses the natural gas, processes the natural gas and/or sells the natural gas to a third party for processing. The Partnership then remits to its producers an agreed-upon percentage of the actual proceeds received from sales of the residue natural gas and NGLs. Certain of these arrangements may also result in returning all or a portion of the residue natural gas and/or the NGLs to the producer, in lieu of returning sales proceeds. The margins earned are directly related to the volume of natural gas that flows through the system and the price at which the Partnership is able to sell the residue natural gas and NGLs. The majority of the Partnership’s contracts have a single performance obligation which is either to provide gathering services (an integrated service) or sell natural gas, NGLs and condensate, which are both satisfied when the related natural gas, crude oil and produced water are received and transferred to an agreed upon delivery point. The Partnership also has certain contracts with multiple performance obligations. They include an option for the customer to acquire additional services such as contracts containing MVCs. These performance obligations would also be satisfied when the related natural gas, crude oil and produced water are received and transferred to an agreed upon delivery point. In these instances, the Partnership allocates the contract’s transaction price to each performance obligation using its best estimate of the standalone selling price of each service in the contract. Performance obligations for gathering services are generally satisfied over time. The Partnership utilizes either an output method (i.e., measure of progress) for guaranteed, stand-ready service contracts or an asset/system delivery time estimate for non-guaranteed, as-available service contracts. Performance obligations for the sale of natural gas, NGLs and condensate are satisfied at a point in time. There are no significant judgments for these transactions because the customer obtains control based on an agreed upon delivery point. Services are typically billed on a monthly basis and the Partnership does not offer extended payment terms. The Partnership does not have contracts with financing components. For the contracts described above, the Partnership reflects its revenues in the financial statement captions described below. Financial statement caption: Revenue description: Revenues: Gathering services and related fees • Revenue earned from fee-based gathering, compression, treating and processing services; Natural gas, NGLs and condensate sales • Revenue from the sale of physical natural gas purchased from customers percent-of- proceeds arrangements (Costs are presented within cost of natural gas and NGLs); • Revenue from sale of condensate and NGLs retained from gathering services (Costs are presented within operation and maintenance expense); and Other revenues • Customer reimbursements to the Partnership for costs incurred by the Partnership on customer’s behalf (Recorded on a gross basis). Certain of the Partnership’s gathering and/or processing agreements provide for monthly or annual MVCs. Under these MVCs, customers agree to ship and/or process a minimum volume of production on its gathering systems or to pay a minimum monetary amount over certain periods during the term of the MVC. A customer must make a shortfall payment to the Partnership at the end of the contracted measurement period if its actual throughput volumes are less than its contractual MVC for that period. Certain customers are entitled to utilize shortfall payments to offset gathering fees in one or more subsequent contracted measurement periods to the extent that such customers throughput volumes in a subsequent contracted measurement period exceed its MVC for that contracted measurement period. The Partnership recognizes customer obligations under their MVCs as revenue and contract assets when (i) it considers it remote that the customer will utilize shortfall payments to offset gathering or processing fees in excess of its MVCs in subsequent periods; (ii) the customer incurs a shortfall in a contract with no banking mechanism or claw back provision; (iii) the customer’s banking mechanism has expired; or (iv) it is remote that the customer will use its unexercised right. In making this determination, the Partnership considers both quantitative and qualitative facts and circumstances, including, but not limited to, contract terms, capacity of the associated pipeline or receipt point and/or expectations regarding future investment, drilling and production. The majority of the Partnership’s revenue is derived from long-term, fee-based contracts with its customers, which include original terms of up to 25 years. The Partnership recognizes revenue earned from fee-based gathering, compression, treating and processing services in gathering services and related fees. The Partnership also earns revenue in the Rockies, Piceance and Permian reporting segments from the sale of physical natural gas purchased from its customers under certain percent-of- proceeds arrangements. Under ASC Topic 606, these gathering contracts are presented net within cost of natural gas and NGLs. The Partnership sells natural gas that it retains from certain customers in the Barnett reporting segment to offset the power expenses of the electric-driven compression on the DFW Midstream system. The Partnership also sells condensate and NGLs retained from certain of its gathering services in the Piceance and Permian 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 the Partnership for costs incurred on their behalf. The Partnership records costs incurred and reimbursed by its customers on a gross basis, with the revenue component recognized in Other revenues. The transaction price in the Partnership’s contracts is primarily based on the volume of natural gas, crude oil or produced water transferred by its gathering systems to the customer’s agreed upon delivery point multiplied by the contractual rate. For contracts that include MVCs, variable consideration up to the MVC will be included in the transaction price. For contracts that do not include MVCs, the Partnership does not estimate variable consideration because the performance obligations are completed and settled on a daily basis. For contracts containing noncash consideration such as fuel received in-kind, the Partnership measures the transaction price at the point of sale when the volume, mix and market price of the commodities are known. The Partnership has contracts with MVCs that are variable and constrained. Contracts with longer than monthly MVCs are reviewed on a quarterly basis and adjustments to those estimates are made during each respective reporting period, if necessary. The transaction price is allocated if the contract contains more than one performance obligation such as contracts that include MVCs. The transaction price allocated is based on the MVC for the applicable measurement period.
Unit-Based Compensation	For awards of unit-based compensation, the Partnership determines a grant date fair value and recognizes the related compensation expense in the statements of operations over the vesting period for each respective award.
Income Taxes	The Partnership is generally not subject to federal and state income taxes, except as noted below. However, its unitholders are individually responsible for paying federal and state income taxes on their share of its taxable income. Net income or loss for GAAP purposes may differ significantly from taxable income reportable to its unitholders as a result of differences between the tax basis and the GAAP basis of assets and liabilities and the taxable income allocation requirements of the Partnership’s governing documents. The aggregate difference in the basis of the Partnership’s net assets for financial and income tax purposes cannot be readily determined as the Partnership does not have access to the information about each partner’s tax attributes related to the Partnership.In general, legal entities that are chartered, organized or conducting business in the state of Texas are subject to a franchise tax (the “Texas Margin Tax”). The Texas Margin Tax has the characteristics of an income tax because it is determined by applying a tax rate to a tax base that considers both revenues and expenses. The Partnership’s financial statements reflect provisions for these tax obligations.
New Accounting Standards Implemented in this Annual Report	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 the Partnership’s consolidated financial statements or 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 the Partnership’s consolidated financial statements or disclosures. New accounting standards not yet implemented in this Annual Report. ASU No. 2020-6 Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815 – 40) (“ASU 2020-6”). ASU 2020-6 simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. The ASU is part of the FASB’s simplification initiative, which aims to reduce unnecessary complexity in GAAP. The ASU’s amendments are effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years. The Partnership is currently evaluating the provisions of ASU 2020-6 to determine its impact on the Partnership’s consolidated financial statements and disclosures. ASU No. 2020-4 Reference Rate Reform (“ASU 2020-4”). ASU 2020-4 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 2020-4 are effective as of March 12, 2020 through December 31, 2022. The Partnership is currently evaluating the provisions of ASU 2020-4 to determine its impact on the Partnership’s consolidated financial statements and disclosures.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Useful lives of Property, Plant and Equipment	Estimates of useful lives follow. Useful lives (In years) Gathering and processing systems and related equipment 12-30 Other 4-15

REVENUE (Tables)

REVENUE (Tables)	12 Months Ended
	Dec. 31, 2021
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 over the remaining contract period related to performance obligations that are unsatisfied and are comprised of estimated MVC shortfall payments. The Partnership applies the practical expedient in paragraph 606-10-50-14 of Topic 606 for certain arrangements that are considered optional purchases (i.e., there is no enforceable obligation for the customer to make purchases) and those amounts are therefore excluded from the table. 2022 2023 2024 2025 2026 Thereafter Gathering services and related fees $ 81,722 $ 63,214 $ 52,412 $ 35,805 $ 21,024 $ —
Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments	In the following table, revenue is disaggregated by geographic area and major products and services. For more detailed information about reportable segments, see Note 18 -Segment Information. Year ended December 31, 2021 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (in thousands) Reportable Segments: Northeast $ 62,567 $ — $ — $ 62,567 Rockies 74,823 48,279 21,985 145,087 Permian 8,230 28,727 3,891 40,848 Piceance 95,235 5,464 4,786 105,485 Barnett 40,850 298 5,443 46,591 Total reportable segments 281,705 82,768 36,105 400,578 Corporate and other — — 40 40 Total $ 281,705 $ 82,768 $ 36,145 $ 400,618 Year ended December 31, 2020 Gathering services and related fees Natural gas, NGLs and condensate sales Other revenues Total (in thousands) Reportable Segments: Northeast $ 62,250 $ — $ — $ 62,250 Rockies 83,107 20,263 17,395 120,765 Permian 10,091 18,857 3,161 32,109 Piceance 106,657 2,612 4,621 113,890 Barnett 40,687 7,587 6,185 54,459 Total reportable segments 302,792 49,319 31,362 383,473 Corporate and other — — — — Total $ 302,792 $ 49,319 $ 31,362 $ 383,473
Schedule of Information about Contract Assets from Contracts with Customers	The following table provides information about contract assets from contracts with customers: December 31, 2021 December 31, 2020 (In thousands) Contract assets, beginning balance $ 2,026 $ 3,902 Additions 9,274 18,834 Transfers out (973) (20,710) Contract assets, ending balance $ 10,327 $ 2,026

PROPERTY, PLANT, AND EQUIPMENT

PROPERTY, PLANT, AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Schedule of property, plant, and equipment, net	Details on the Partnership’s property, plant and equipment follow. December 31, 2021 December 31, 2020 (In thousands) Gathering and processing systems and related equipment $ 2,225,267 $ 2,213,501 Construction in progress 49,082 60,443 Land and line fill 10,644 10,440 Other 51,863 51,276 Total 2,336,856 2,335,660 Less accumulated depreciation (610,774) (521,850) Property, plant and equipment, net $ 1,726,082 $ 1,813,810
Schedule of depreciation expense and capitalized interest costs	Depreciation expense and capitalized interest for the Partnership follow. Year ended December 31, 2021 2020 (In thousands) Depreciation expense $ 90,711 $ 86,263 Capitalized interest 1,534 $ 3,878

AMORTIZING INTANGIBLE ASSETS (T

AMORTIZING INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets and liabilities subject to amortization	Details regarding the Partnership’s intangible assets, all of which are subject to amortization, follow. December 31, 2021 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (17,002) $ 7,193 Contract intangibles 278,448 (217,245) 61,203 Rights-of-way 159,916 (55,385) 104,531 Total intangible assets $ 462,559 $ (289,632) $ 172,927 December 31, 2020 Gross carrying amount Accumulated amortization Net (In thousands) Favorable gas gathering contracts $ 24,195 $ (16,064) $ 8,131 Contract intangibles 278,448 (195,243) 83,205 Rights-of-way 157,271 (49,041) 108,230 Total intangible assets $ 459,914 $ (260,348) $ 199,566
Recognized amortization expense in other revenues and cost and expenses	The Partnership recognized amortization expense of its favorable gas gathering contracts in Other revenues as follows: Year ended December 31, 2021 2020 (In thousands) Amortization expense – favorable gas gathering contracts $ 938 $ 938 The Partnership recognized amortization expense of its contract and right of way intangibles in costs and expenses as follows: Year ended December 31, 2021 2020 (In thousands) Amortization expense – contract intangibles $ 22,002 $ 25,694 Amortization expense – rights-of-way 6,344 6,175
Estimated aggregate annual amortization expected to be recognized	The Partnership’s estimated aggregate annual amortization expected to be recognized as of December 31, 2021 for each of the five succeeding fiscal years follows. (In thousands) 2022 $ 25,466 2023 25,412 2024 15,241 2025 15,057 2026 12,034 Thereafter 79,717 $ 172,927

EQUITY METHOD INVESTMENTS (Tabl

EQUITY METHOD INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Details of the Partnership’s equity method investments follows. December 31, 2021 December 31, 2020 (In thousands) Double E $ 280,952 $ 132,852 Ohio Gathering 242,244 259,888 Total $ 523,196 $ 392,740 Summarized balance sheet information for Double E follows (amounts represent 100% of investee financial information). December 31, 2021 December 31, 2020 (In thousands) Current assets $ 12,353 $ 3,060 Noncurrent assets 410,731 197,463 Total assets $ 423,084 $ 200,523 Current liabilities $ 22,836 $ 12,479 Noncurrent liabilities 10,281 4,452 Total liabilities $ 33,117 $ 16,931 Summarized statements of operations information for Double E follows (amounts represent 100% of investee financial information). Year ended December 31, 2021 Year Ended December 31, 2020 (In thousands) Total revenues $ 3,579 $ — Total operating expenses 5,281 2,604 Net income (loss) $ (1,702) $ (2,604) A reconciliation of the difference between the carrying amount of the Partnership’s interest in Ohio Gathering and the Partnership’s underlying investment in Ohio Gathering, per Ohio Gathering’s books and records, is shown below. 2021 2020 (In thousands) Investment in Ohio Gathering, December 31 $ 242,244 $ 259,888 December cash distributions 2,222 2,748 Impairment loss 1,971 — Basis difference 207,927 216,591 Other 137 — Investment in Ohio Gathering (Books and records), November 30, $ 454,501 $ 479,227 Summarized balance sheet information for OGC and OCC follows (amounts represent 100% of investee financial information). November 30, 2021 November 30, 2020 OGC OCC OGC OCC (In thousands) Current assets $ 36,967 $ 5,300 $ 32,404 $ 4,902 Noncurrent assets 1,189,921 961 1,240,090 290 Total assets $ 1,226,888 $ 6,261 $ 1,272,494 $ 5,192 Current liabilities $ 7,984 $ 3,104 $ 8,424 $ 2,982 Noncurrent liabilities 9,854 4,927 8,441 5,146 Total liabilities $ 17,838 $ 8,031 $ 16,865 $ 8,128 Summarized statements of operations information for OGC and OCC follows (amounts represent 100% of investee financial information). Twelve months ended Twelve months ended OGC OCC OGC OCC (In thousands) Total revenues $ 102,140 $ 12,614 $ 114,524 $ 12,931 Total operating expenses 95,399 11,419 103,020 38,502 Net income (loss) 6,742 1,169 11,496 (25,571)

DEFERRED REVENUE (Tables)

DEFERRED REVENUE (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Rollforward of deferred revenue	A rollforward of current deferred revenue follows. (In thousands) Current deferred revenue, January 1, 2021 $ 9,988 Additions 6,956 Less: revenue recognized (6,570) Current deferred revenue, December 31, 2021 $ 10,374 A rollforward of noncurrent deferred revenue follows. (In thousands) Noncurrent deferred revenue, January 1, 2021 $ 48,250 Additions 1,304 Less: reclassification to current deferred revenue (6,984) Noncurrent deferred revenue, December 31, 2021 $ 42,570

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Schedule of debt and capital leases	Debt for the Partnership at December 31, 2021 and 2020 follows. December 31, 2021 December 31, 2020 (In thousands) Revolving Credit Facility : Summit Holdings' variable rate senior secured revolving credit facility due May 13, 2022 (1) $ — $ 857,000 ABL Facility : Summit Holdings' asset based credit facility due May 1, 2026 267,000 — Permian Transmission Credit Facility : Permian Transmission's variable rate senior secured credit facility due March 8, 2028 160,000 — 2022 Senior Notes : Summit Holdings' 5.5% senior unsecured notes due August 15, 2022 (2) — 234,047 2025 Senior Notes : Summit Holdings' 5.75% senior unsecured notes due April 15, 2025 259,463 259,463 2026 Secured Notes : Summit Holdings' and Finance Corp's 8.50% senior unsecured second lien notes due October 15, 2026 700,000 — Less: unamortized debt discount and debt issuance costs (31,391) (3,184) Total long-term debt $ 1,355,072 $ 1,347,326 _______________________________________ (1) The Revolving Credit Facility was repaid in full in November 2021. (2) The 2022 Senior Notes were repaid in full in November 2021.
Schedule of maturities of long-term debt	The aggregate amount of Partnership’s debt maturing during each of the years after December 31, 2021 are as follows (in thousands): 2022 $ — 2023 — 2024 — 2025 259,463 2026 967,000 Thereafter 160,000 Total long-term debt $ 1,386,463

LIABILITY MANAGEMENT TRANSACT_2

LIABILITY MANAGEMENT TRANSACTIONS (Tables)	12 Months Ended
	Dec. 31, 2021
Liability Management Transactions [Abstract]
Schedule of extinguishment of debt	The Partnership recognized a $203.1 million gain on extinguishment of debt during the year ended December 31, 2020, the components of which are summarized in the table below. ECP Loan Open Market Tender TL Total 2022 2025 2022 2025 (in thousands) Senior Notes Senior Notes Senior Notes Senior Notes Gain on Repurchases of Senior Notes and TL Restructuring $ — $ 11,554 $ 76,789 $ 9,223 $ 15,479 $ 99,175 $ 212,220 Debt issue costs (361) (143) (1,541) (125) (351) (2,724) (5,245) Transaction costs (249) (105) (105) (467) (467) (2,520) (3,913) Gain (loss) on debt extinguishment $ (610) $ 11,306 $ 75,143 $ 8,631 $ 14,661 $ 93,931 $ 203,062

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of accrued environmental remediation	A rollforward of the Partnership’s undiscounted accrued environmental remediation follows and is primarily related to the 2015 Blacktail Release and other environmental remediation activities is below. (In thousands) Accrued environmental remediation, January 1, 2020 $ 4,651 Payments made (1,722) Accrued environmental remediation, December 31, 2020 $ 2,929 Payments made (1,972) Additional accruals 4,649 Accrued environmental remediation, December 31, 2021 $ 5,606

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Summary of the estimated fair value of debt instruments	A summary of the estimated fair value of the Partnerships debt financial instruments follows. December 31, 2021 December 31, 2020 Carrying Value (1) Estimated Carrying Value (1) Estimated (in thousands) 2022 Senior Notes $ — $ — $ 234,047 $ 215,713 2025 Senior Notes 259,463 234,814 259,463 168,002 2026 Secured Notes 700,000 718,083 — — (1) Excludes applicable unamortized debt issuance costs and debt discounts.

PARTNERS' CAPITAL AND MEZZANI_2

PARTNERS' CAPITAL AND MEZZANINE CAPITAL (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Schedule of partner units activity	A rollforward of the number of common limited partner units follows for the period from December 31, 2019 to December 31, 2021. Common Units (2) December 31, 2019 3,021,258 GP Buy-In Transaction (1) (132,687) Common units issued for SMLP LTIP, net 95,987 TL Restructuring 2,306,972 Series A Preferred Unit Exchange Offer, net of units withheld for taxes 817,845 Other 717 December 31, 2020 6,110,092 2021 Preferred Exchange Offer, net of units withheld for taxes 538,715 Common units issued for SMLP LTIP, net 106,580 ECP Warrant Exercise 414,447 December 31, 2021 7,169,834 (1) The purchase price for the SMLP common units reflected in the consolidated statement of partners’ capital for the year ended December 31, 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 0.7 million warrants, and (iii) $6.8 million of advisory fees and other direct costs related to closing the GP Buy-In Transaction. (2) As adjusted for reverse unit split. A rollforward of the number of Series A Preferred Units follows for the period from December 31, 2019 to December 31, 2021. Series A December 31, 2019 300,000 Series A Preferred Unit Exchange Offer (62,816) Series A Preferred Unit Tender (75,075) December 31, 2020 162,109 Series A Preferred Unit Exchange Offer (18,662) December 31, 2021 143,447
Change in subsidiary	The following table shows the change in the Partnership’s Subsidiary Series A Preferred Unit balance during the year ended December 31, 2021: (in thousands) Balance at January 1, 2020 $ 27,450 New issuances 50,000 PIK distributions 5,251 Issuance costs (1,290) Redemption accretion 8,247 Balance at December 31, 2020 $ 89,658 PIK distributions 6,131 Redemption accretion 10,536 Balance at December 31, 2021 (1) $ 106,325 (1) Amount is net of $3.9 million of issuance costs at December 31, 2021.

EARNINGS PER UNIT (Tables)

EARNINGS PER UNIT (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of earnings per limited partner unit	The following table details the components of EPU. Year ended December 31, 2021 2020 (In thousands, except per-unit amounts) Numerator for basic and diluted EPU: Allocation of net income (loss) among limited partner interests: Net income (loss) $ (19,949) $ 189,078 Net income attributable to Subsidiary Series A Preferred Units (16,667) (13,498) Net loss attributable to noncontrolling interest — 3,274 Net income (loss) attributable Summit Midstream Partners, LP (36,616) 178,854 Less: Net income attributable to Series A Preferred Unit (15,998) (26,529) Add: Deemed capital contribution 8,326 110,669 Net income (loss) attributable to common limited partners $ (44,288) $ 262,994 Denominator for basic and diluted EPU: Weighted-average common units outstanding – basic 6,741 3,592 Effect of nonvested phantom units — 102 Weighted-average common units outstanding – diluted 6,741 3,694 Net Income (Loss) per limited partner unit: Common unit – basic $ (6.57) $ 73.22 Common unit – diluted $ (6.57) $ 71.19 Nonvested anti-dilutive phantom units excluded from the calculation of diluted EPU 203 240

SUPPLEMENTAL CASH FLOW INFORM_2

SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2021
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flow information	Year ended December 31, 2021 2020 (In thousands) Supplemental cash flow information: Cash interest paid $ 57,655 $ 79,450 Cash paid for taxes $ 191 $ 190 Noncash investing and financing activities: Capital expenditures in trade accounts payable (period-end accruals) $ 5,692 $ 6,154 Warrant issuance for GP Buy-In Transaction — 2,300 Right-of-use assets relating to ASC Topic 842 — 3,685 Fair value of SMLP equity for TL Restructuring — 30,521 Accretion of Subsidiary Series A Preferred Units 10,536 8,247 Exercise of ECP Warrants 15,542 —

UNIT-BASED AND NONCASH COMPEN_2

UNIT-BASED AND NONCASH COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Schedule of activity	The following table presents phantom unit activity for the periods presented: Units Weighted-average grant date fair value Nonvested phantom units, December 31, 2019 140,400 $ 115.35 Phantom units granted 345,997 9.20 Phantom units vested (193,349) 54.07 Phantom units forfeited (1,357) 119.24 Nonvested phantom units, December 31, 2020 291,691 26.57 Phantom units granted 199,241 22.33 Phantom units vested (143,768) 30.66 Phantom units forfeited (13,385) 38.85 Nonvested phantom units, December 31, 2021 333,779 $ 21.78
Schedule of intrinsic values	The intrinsic value of phantom units that vested during the years ended December 31, follows. Year ended December 31, 2021 2020 (In thousands) Intrinsic value of vested LTIP awards $ 4,407 $ 2,602
Schedule of unit-based compensation recognized in general and administrative expense	Unit-based compensation recognized in general and administrative expense related to awards under the SMLP LTIP follows. Year ended December 31, 2021 2020 (In thousands) SMLP LTIP unit-based compensation $ 4,744 $ 8,111

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of right-of-use assets and lease liabilities	ROU assets (included in the other noncurrent assets Other current liabilities Other noncurrent liabilities December 31, 2021 December 31, 2020 (In thousands) ROU assets Operating $ 2,515 $ 3,736 Finance 792 1,748 $ 3,307 $ 5,484 Lease liabilities, current Operating $ 1,213 $ 2,298 Finance 167 618 $ 1,380 $ 2,916 Lease liabilities, noncurrent Operating $ 2,272 $ 3,182 Finance 122 154 $ 2,394 $ 3,336
Schedule of lease cost and other information	Lease cost and Other information follow: Year ended December 31, 2021 2020 (In thousands) Lease cost Finance lease cost: Amortization of ROU assets (included in depreciation and amortization) $ 1,026 $ 1,274 Interest on lease liabilities (included in interest expense) 20 52 Operating lease cost (included in general and administrative expense) 1,722 2,644 $ 2,768 $ 3,970 Year ended December 31, 2021 2020 (In thousands) Other information Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows from operating leases $ 1,407 $ 1,472 Operating cash outflows from finance leases 20 52 Financing cash outflows from finance leases 634 1,150 ROU assets obtained in exchange for new operating lease liabilities — 3,552 ROU assets obtained in exchange for new finance lease liabilities 94 133 Weighted-average remaining lease term (years) - operating leases 5.1 4.9 Weighted-average remaining lease term (years) - finance leases 1.1 1.4 Weighted-average discount rate - operating leases 5 % 5 % Weighted-average discount rate - finance leases 4 % 4 % The Partnership recognizes total lease expense incurred or allocated to us in general and administrative expenses. Lease expense related to operating leases, including lease expense incurred on the Partnership’s behalf and allocated to us, was as follows: Year ended December 31, 2021 2020 (In thousands) Lease expense $ 2,479 $ 3,436
Future minimum lease payments due and future minimum rentals to be received under noncancelable leases and subleases	Future minimum lease payments due under noncancelable leases at December 31, 2021, were as follows: December 31, 2021 (In thousands) Operating Finance 2022 $ 1,173 $ 173 2023 854 88 2024 573 38 2025 464 — 2026 156 — 2027 160 — Thereafter 418 — Total future minimum lease payments $ 3,798 $ 299

RESTRUCTURING (Tables)

RESTRUCTURING (Tables)	12 Months Ended
	Dec. 31, 2021
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	Details for the 2020 and 2019 Restructuring Plans follow. Severance Charges Other Restructuring Charges Total Severance and Other 2021 2020 2021 2020 2021 2020 (In thousands) 2020 Restructuring Plan $ 810 $ 5,591 $ 104 $ 56 $ 914 $ 5,647 2019 Restructuring Plan — 2,159 — 1,293 — 3,452 $ 810 $ 7,750 $ 104 $ 1,349 $ 914 $ 9,099 Accrued December 31, 2019 Charges Incurred Cash Payments Accrued December 31, 2020 Charges Incurred Cash Payments Accrued December 31, 2021 (In thousands) Employee-related costs $ 2,816 $ 7,750 $ (7,018) $ 3,548 $ 810 $ (4,358) $ — Other — 1,349 (1,349) — 104 (104) — Total restructuring costs $ 2,816 $ 9,099 $ (8,367) $ 3,548 $ 914 $ (4,462) $ —

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Schedule of assets by reportable segment	Assets by reportable segment follow. December 31, 2021 2020 (in thousands) Assets: Northeast $ 623,224 $ 645,754 Rockies 592,148 625,793 Permian 458,988 299,421 Piceance 524,218 579,800 Barnett 315,055 336,629 Total reportable segment assets 2,513,633 2,487,397 Corporate and Other 8,829 12,420 Total assets $ 2,522,462 $ 2,499,817
Schedule of segment reporting information	Revenues by reportable segment follow. Year ended December 31, 2021 2020 (In thousands) Revenues: Northeast $ 62,567 $ 62,250 Rockies 145,087 120,765 Permian 40,848 32,109 Piceance 105,485 113,890 Barnett 46,591 54,459 Total reportable segments revenue 400,578 383,473 Corporate and Other 40 — Total revenues $ 400,618 $ 383,473 Depreciation and amortization, including the amortization expense associated with the Partnership’s favorable and unfavorable gas gathering contracts as reported in other revenues, by reportable segment follows. Year ended December 31, 2021 2020 (In thousands) Depreciation and amortization: Northeast $ 17,054 $ 16,891 Rockies 29,513 32,057 Permian 5,858 5,455 Piceance 48,773 45,203 Barnett (1) 16,133 16,112 Total reportable segment depreciation and amortization 117,331 115,718 Corporate and Other 2,664 3,352 Total depreciation and amortization $ 119,995 $ 119,070 ______________________________________ (1) Includes the amortization expense associated with the Partnership’s favorable and unfavorable gas gathering contracts as reported in Other revenues. Cash paid for capital expenditures by reportable segment follow. Year ended December 31, 2021 2020 (In thousands) Cash paid for capital expenditures: Northeast $ 11,237 $ 7,657 Rockies 9,875 21,596 Permian 2,042 7,014 Piceance 579 1,370 Barnett 766 1,878 Total reportable segment capital expenditures 24,499 39,515 Corporate and Other 531 3,613 Total cash paid for capital expenditures $ 25,030 $ 43,128
Schedule of counterparties accounting for more than 10% of total revenues	Counterparties accounting for a significant portion of total revenues were as follows: Year ended December 31, 2021 2020 Percentage of total revenues (1) : Counterparty A - Piceance 12 % 13 % Counterparty B - Northeast * 5 % Counterparty B - Permian * 5 % Counterparty B - Barnett * 1 % ________________________________________________________ * Less than 10% in the aggregate
Reconciliation of net income to adjusted EBITDA	Segment adjusted EBITDA by reportable segment follows. Year ended December 31, 2021 2020 (In thousands) Reportable segment adjusted EBITDA Northeast $ 83,287 $ 85,854 Rockies 64,517 71,509 Permian 6,614 5,744 Piceance 76,131 88,820 Barnett 36,729 32,093 Total of reportable segments' measures of profit $ 267,278 $ 284,020 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. Year ended December 31, 2021 2020 (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 $ (28,156) $ 177,661 Add: Corporate and Other expense 68,783 60,903 Interest expense 66,156 78,894 Gain on early extinguishment of debt 3,523 (203,062) Depreciation and amortization (1) 119,995 119,070 Proportional adjusted EBITDA for equity method investees 29,022 31,056 Adjustments related to capital reimbursement activity (6,571) (1,395) Unit-based and noncash compensation 4,744 8,111 Gain on asset sales, net (369) (307) Long-lived asset impairment 10,151 13,089 Total of reportable segments' measures of profit $ 267,278 $ 284,020 ______________________________________ (1) Includes the amortization expense associated with the Partnership’s favorable gas gathering contracts as reported in other revenues.

ORGANIZATION, BUSINESS OPERAT_2

ORGANIZATION, BUSINESS OPERATIONS AND PRESENTATION AND CONSOLIDATION (Details) $ in Millions	Nov. 09, 2020shares	Dec. 31, 2021USD ($)shares	Dec. 31, 2020shares
Organization And Business Operations [Line Items]
Common limited partner capital (in shares)		7,169,834	6,110,092
Summit Midstream GP, LLC | Reverse Unit Split
Organization And Business Operations [Line Items]
Common limited partner capital (in shares)	56,624,887	3,774,992
Common units | Energy Capital Partners
Organization And Business Operations [Line Items]
Common limited partner capital (in shares)		0.4
Summit Midstream Partners Holdings L L C
Organization And Business Operations [Line Items]
SMLP common units pledged as collateral under the SMPH Term Loan (in shares)		2,300,000
SMLP common units not pledged as collateral under the SMPH Term Loan (in shares)		700,000
Common units retire (in shares)		1,100,000
Reverse unit split ratio	0.07
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 (in shares)		700,000

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Summary of Significant Accounting Policies [Line Items]
Restricted cash	$ 12,223	$ 0
Favorable gas gathering contracts | Minimum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	10 years
Favorable gas gathering contracts | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	20 years
Other Gas Gathering Contract | Minimum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	3 years
Other Gas Gathering Contract | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	25 years
Rights-of-way | Minimum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	20 years
Rights-of-way | Maximum
Summary of Significant Accounting Policies [Line Items]
Useful lives (In years)	30 years

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2021
Gathering and processing systems and related equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life	12 years
Gathering and processing systems and related equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life	30 years
Other | Minimum
Property, Plant and Equipment [Line Items]
Useful life	4 years
Other | Maximum
Property, Plant and Equipment [Line Items]
Useful life	15 years

REVENUE - Remaining Performance

REVENUE - Remaining Performance Obligation Period (Details) - Gathering services and related fees	Dec. 31, 2021
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, 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, 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, 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	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
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, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, Period	1 year

REVENUE - Remaining Performan_2

REVENUE - Remaining Performance Obligation Amount (Details) - Gathering services and related fees $ in Thousands	Dec. 31, 2021USD ($)
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	$ 81,722
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	63,214
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	52,412
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	35,805
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	21,024
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation	$ 0

REVENUE - Schedule of Disaggreg

REVENUE - Schedule of Disaggregated Revenue by Geographic Area and Major Products and Services Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 400,618	$ 383,473
All Other Segments
Disaggregation of Revenue [Line Items]
Total revenues	40	0
Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	400,578	383,473
Reportable Segments | Northeast
Disaggregation of Revenue [Line Items]
Total revenues	62,567	62,250
Reportable Segments | Rockies
Disaggregation of Revenue [Line Items]
Total revenues	145,087	120,765
Reportable Segments | Permian
Disaggregation of Revenue [Line Items]
Total revenues	40,848	32,109
Reportable Segments | Piceance
Disaggregation of Revenue [Line Items]
Total revenues	105,485	113,890
Reportable Segments | Barnett
Disaggregation of Revenue [Line Items]
Total revenues	46,591	54,459
Gathering services and related fees
Disaggregation of Revenue [Line Items]
Total revenues	281,705	302,792
Gathering services and related fees | All Other Segments
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Gathering services and related fees | Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	281,705	302,792
Gathering services and related fees | Reportable Segments | Northeast
Disaggregation of Revenue [Line Items]
Total revenues	62,567	62,250
Gathering services and related fees | Reportable Segments | Rockies
Disaggregation of Revenue [Line Items]
Total revenues	74,823	83,107
Gathering services and related fees | Reportable Segments | Permian
Disaggregation of Revenue [Line Items]
Total revenues	8,230	10,091
Gathering services and related fees | Reportable Segments | Piceance
Disaggregation of Revenue [Line Items]
Total revenues	95,235	106,657
Gathering services and related fees | Reportable Segments | Barnett
Disaggregation of Revenue [Line Items]
Total revenues	40,850	40,687
Natural gas, NGLs and condensate sales
Disaggregation of Revenue [Line Items]
Total revenues	82,768	49,319
Natural gas, NGLs and condensate sales | All Other Segments
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Natural gas, NGLs and condensate sales | Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	82,768	49,319
Natural gas, NGLs and condensate sales | Reportable Segments | Northeast
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Natural gas, NGLs and condensate sales | Reportable Segments | Rockies
Disaggregation of Revenue [Line Items]
Total revenues	48,279	20,263
Natural gas, NGLs and condensate sales | Reportable Segments | Permian
Disaggregation of Revenue [Line Items]
Total revenues	28,727	18,857
Natural gas, NGLs and condensate sales | Reportable Segments | Piceance
Disaggregation of Revenue [Line Items]
Total revenues	5,464	2,612
Natural gas, NGLs and condensate sales | Reportable Segments | Barnett
Disaggregation of Revenue [Line Items]
Total revenues	298	7,587
Other revenues
Disaggregation of Revenue [Line Items]
Total revenues	36,145	31,362
Other revenues | All Other Segments
Disaggregation of Revenue [Line Items]
Total revenues	40	0
Other revenues | Reportable Segments
Disaggregation of Revenue [Line Items]
Total revenues	36,105	31,362
Other revenues | Reportable Segments | Northeast
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Other revenues | Reportable Segments | Rockies
Disaggregation of Revenue [Line Items]
Total revenues	21,985	17,395
Other revenues | Reportable Segments | Permian
Disaggregation of Revenue [Line Items]
Total revenues	3,891	3,161
Other revenues | Reportable Segments | Piceance
Disaggregation of Revenue [Line Items]
Total revenues	4,786	4,621
Other revenues | Reportable Segments | Barnett
Disaggregation of Revenue [Line Items]
Total revenues	$ 5,443	$ 6,185

REVENUE - Schedule of Informati

REVENUE - Schedule of Information about Contract Assets from Contracts with Customers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Abstract]
Contract assets, beginning of period	$ 2,026	$ 3,902
Additions	9,274	18,834
Transfers out	(973)	(20,710)
Contract assets, end of period	$ 10,327	$ 2,026

REVENUE - Narrative (Details)

REVENUE - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue From Contract With Customer [Line Items]
Receivables with customers	$ 50,500	$ 57,500
Contract assets included in accounts receivable	$ 10,327	$ 2,026	$ 3,902

PROPERTY, PLANT, AND EQUIPMEN_2

PROPERTY, PLANT, AND EQUIPMENT - Schedule of Property, Plant, and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,336,856	$ 2,335,660
Less accumulated depreciation	(610,774)	(521,850)
Property, plant and equipment, net	1,726,082	1,813,810
Gathering and processing systems and related equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,225,267	2,213,501
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	49,082	60,443
Land and line fill
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,644	10,440
Other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 51,863	$ 51,276

PROPERTY, PLANT, AND EQUIPMEN_3

PROPERTY, PLANT, AND EQUIPMENT - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Impairment of property, plant and equipment	$ 10.2	$ 13.1

PROPERTY, PLANT, AND EQUIPMEN_4

PROPERTY, PLANT, AND EQUIPMENT - Schedule of Depreciation Expense and Capitalized Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 90,711	$ 86,263
Capitalized interest	$ 1,534	$ 3,878

AMORTIZING INTANGIBLE ASSETS -

AMORTIZING INTANGIBLE ASSETS - Intangible Assets and Liabilities Subject to Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 462,559	$ 459,914
Accumulated amortization	(289,632)	(260,348)
Net	172,927	199,566
Favorable gas gathering contracts
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	24,195	24,195
Accumulated amortization	(17,002)	(16,064)
Net	7,193	8,131
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	278,448	278,448
Accumulated amortization	(217,245)	(195,243)
Net	61,203	83,205
Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	159,916	157,271
Accumulated amortization	(55,385)	(49,041)
Net	$ 104,531	$ 108,230

AMORTIZING INTANGIBLE ASSETS _2

AMORTIZING INTANGIBLE ASSETS - Recognized Amortization Expense in Other Revenues and Cost and Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Other Revenue | Favorable gas gathering contracts
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 938	$ 938
Costs And Expenses | Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization expense	22,002	25,694
Costs And Expenses | Rights-of-way
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 6,344	$ 6,175

AMORTIZING INTANGIBLE ASSETS _3

AMORTIZING INTANGIBLE ASSETS - Estimated Aggregate Annual Amortization Expected to be Recognized (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
2022	$ 25,466
2023	25,412
2024	15,241
2025	15,057
2026	12,034
Thereafter	79,717
Net	$ 172,927	$ 199,566

EQUITY METHOD INVESTMENTS - Sch

EQUITY METHOD INVESTMENTS - Schedule of Equity Method Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	$ 523,196	$ 392,740
Double E
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	280,952	132,852
Ohio Gathering
Schedule of Equity Method Investments [Line Items]
Investment in equity method investees	$ 242,244	$ 259,888

EQUITY METHOD INVESTMENTS - Nar

EQUITY METHOD INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Double E
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest	70.00%
Investment in Double E equity method investee	$ (148,699)	$ (99,927)
Capitalized interest paid	$ 3,000	$ 2,700
Ohio Gathering | Principal Owner
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest	38.00%

EQUITY METHOD INVESTMENTS - Rol

EQUITY METHOD INVESTMENTS - Rollforward of the Investment in Equity Method Investees (Details) - USD ($) $ in Thousands	11 Months Ended		12 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Equity Method Investment [Roll Forward]
Beginning balance	$ 392,740		$ 392,740
December cash distributions			26,760	$ 28,185
Ending balance			523,196	392,740
Ohio Gathering
Equity Method Investment [Roll Forward]
Beginning balance	259,888		259,888
Ending balance			242,244	259,888
Ohio Gathering | Summit Midstream Partners, LLC
Equity Method Investment [Roll Forward]
Beginning balance	242,244	$ 259,888	$ 242,244	259,888
December cash distributions	2,222	2,748
Impairment loss	1,971	0
Basis difference	207,927	216,591
Other	137	0
Ending balance	$ 454,501	$ 479,227		$ 242,244

EQUITY METHOD INVESTMENTS - Bal

EQUITY METHOD INVESTMENTS - Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Nov. 30, 2021	Dec. 31, 2020	Nov. 30, 2020
Schedule of Equity Method Investments [Line Items]
Current assets	$ 87,369		$ 82,099
TOTAL ASSETS	2,522,462		2,499,817
Current liabilities	79,237		68,408
Total liabilities	1,511,774		1,487,268
Ohio Gathering | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Current assets		$ 36,967		$ 32,404
Noncurrent assets		1,189,921		1,240,090
TOTAL ASSETS		1,226,888		1,272,494
Current liabilities		7,984		8,424
Noncurrent liabilities		9,854		8,441
Total liabilities		17,838		16,865
OCC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Current assets		5,300		4,902
Noncurrent assets		961		290
TOTAL ASSETS		6,261		5,192
Current liabilities		3,104		2,982
Noncurrent liabilities		4,927		5,146
Total liabilities		$ 8,031		$ 8,128
Double E
Schedule of Equity Method Investments [Line Items]
Current assets	12,353		3,060
Noncurrent assets	410,731		197,463
TOTAL ASSETS	423,084		200,523
Current liabilities	22,836		12,479
Noncurrent liabilities	10,281		4,452
Total liabilities	$ 33,117		$ 16,931

EQUITY METHOD INVESTMENTS - Sta

EQUITY METHOD INVESTMENTS - Statements of Operations Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Nov. 30, 2021	Dec. 31, 2020	Nov. 30, 2020
Schedule of Equity Method Investments [Line Items]
Result of operations	$ 3,579		$ 0
Total operating expenses	5,281		2,604
Net income (loss)	(19,949)		189,078
Ohio Gathering | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Result of operations		$ 102,140		$ 114,524
Total operating expenses		95,399		103,020
Net income (loss)		6,742		11,496
OCC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Result of operations		12,614		12,931
Total operating expenses		11,419		38,502
Net income (loss)		$ 1,169		$ (25,571)
Double E
Schedule of Equity Method Investments [Line Items]
Net income (loss)	$ (1,702)		$ (2,604)

DEFERRED REVENUE (Details)

DEFERRED REVENUE (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Change in Contract With Customer, Liability, Current [Roll Forward]
Beginning balance	$ 9,988
Additions	6,956
Less: revenue recognized	(6,570)
Ending balance	10,374
Change in Contract With Customer, Liability, Noncurrent [Roll Forward]
Beginning balance	48,250
Additions	1,304
Less: reclassification to current deferred revenue	(6,984)
Ending balance	$ 42,570

DEBT - Components of Long-Term

DEBT - Components of Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Total long-term debt	$ 1,355,072	$ 1,347,326
Senior Secured Revolving Credit Facility Due May 2022
Line of Credit Facility [Line Items]
Revolving credit facility	0	857,000
Asset Backed Lending Facility
Line of Credit Facility [Line Items]
Line of credit facility, outstanding amount	267,000	0
Permian Transmission Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, outstanding amount	160,000	0
2022 Senior Notes
Line of Credit Facility [Line Items]
Unsecured notes	$ 0	234,047
Stated interest rate (as a percent)	5.50%
2025 Senior Notes
Line of Credit Facility [Line Items]
Unsecured notes	$ 259,463	259,463
Stated interest rate (as a percent)	5.75%
2026 Secured Notes
Line of Credit Facility [Line Items]
Less unamortized debt issuance costs	$ (31,391)	(3,184)
Unsecured notes	$ 700,000	$ 0
Stated interest rate (as a percent)	8.50%

DEBT - Schedule of Maturities (

DEBT - Schedule of Maturities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Debt
2022	$ 0
2023	0
2024	0
2025	259,463
2026	967,000
Thereafter	160,000
Total long-term debt	$ 1,386,463

DEBT - Narrative (Details)

DEBT - Narrative (Details)	Nov. 02, 2021USD ($)	Nov. 17, 2020USD ($)shares	Aug. 07, 2020USD ($)	Dec. 31, 2021USD ($)	Mar. 08, 2021USD ($)	Dec. 31, 2020USD ($)	May 28, 2020USD ($)
Debt Instrument [Line Items]
Total debt				$ 1,355,072,000		$ 1,347,326,000
Term Loan
Debt Instrument [Line Items]
Stated interest rate (as a percent)							8.00%
Repayments of debt			$ 35,000,000
Repayments of accrued interest			$ 600,000
Liability Management Transactions | SMPH Term Loan Restructuring
Debt Instrument [Line Items]
Term Loan result in consensual debt discharge of full amount owed under Term Loan exchange		$ 155,200,000
Capital stock issued		$ 2,300,000
Common stock held (in shares) | shares		2,306,972
Cash payment on the deferred purchase price obligation		$ 26,500,000
Liability Management Transactions | SMPH Term Loan Restructuring | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		6.00%
Liability Management Transactions | SMPH Term Loan Restructuring | ABR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		5.00%
ABL Facility
Debt Instrument [Line Items]
Borrowing capacity	$ 400,000,000
Borrowing base				$ 691,200,000
Interest rate (as a percent)				3.38%
Unused portion under the facility				$ 109,100,000
Debt Instrument, Covenant, Maximum Amount Outstanding For Maturity	$ 50,000,000
Debt Instrument, Covenant, Mandatory Redemption Period	120 days
Debt Instrument, Covenant, First Lien Net Leverage Ratio	2.50			1.10
Debt Instrument, Covenant, Interest Coverage Ratio	2			4.30
ABL Facility | Standby Letters of Credit
Debt Instrument [Line Items]
Line of credit facility, outstanding amount				$ 23,900,000
ABL Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				3.25%
2025 Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Covenant, Maximum Amount Outstanding For Maturity	$ 50,000,000
Deferred issuance costs				$ 7,700,000
2025 Senior Notes | Redemption period two | Summit Holdings and Finance Corporation
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount				102.875%
2025 Senior Notes | Redemption period three | Summit Holdings and Finance Corporation
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount				100.00%
Credit Agreement
Debt Instrument [Line Items]
Borrowing capacity					$ 175,000,000
Debt Instrument, Interest Rate, Effective Percentage				2.50%
Debt Instrument, Unused Borrowing Capacity, Amount				$ 13,000,000
Credit Agreement | Standby Letters of Credit
Debt Instrument [Line Items]
Total debt				$ 2,000,000
Credit Agreement | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)				2.375%
Line of Credit Facility, Commitment Fee Percentage				0.70%
Credit Agreement | Term Loan Credit Facility
Debt Instrument [Line Items]
Borrowing capacity					160,000,000
Credit Agreement | Working Capital Credit Facility
Debt Instrument [Line Items]
Borrowing capacity					$ 15,000,000
2026 Notes
Debt Instrument [Line Items]
Debt instrument, amount				$ 700,000,000
Stated interest rate (as a percent)				8.50%
Debt Instrument, Issued As A Percentage of Face Value				98.50%
Secured Notes Indenture, 2026
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	35.00%
Redemption price, expressed as percentage of principal amount	108.50%
Debt Instrument, Covenant, Redemption, Percent of Initial Principal Amount Remaining Outstanding	65.00%
Debt Instrument, Covenant, Ownership Percentage of Principal	25.00%
Debt Instrument, Covenant, Repurchase Amount Of Principal Plus Accrued Interest	100.00%
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Period Three	$ 200,000,000
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Period One	$ 50,000,000
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Basis Point Increase, Period One	0.50%
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Period Two	$ 100,000,000
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Basis Point Increase, Period Two	1.00%
Debt Instrument, Covenant, Excess Cash Flow Offer To Purchase, Basis Point Increase, Period Three	2.00%
Secured Notes Indenture, 2026 | Redemption period one
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	104.25%
Secured Notes Indenture, 2026 | Redemption period two
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	102.125%
Secured Notes Indenture, 2026 | Redemption period three
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount	100.00%
2022 Senior Notes
Debt Instrument [Line Items]
Redemption price, expressed as percentage of principal amount				100.00%
ECP NewCo Loan | Term Loan
Debt Instrument [Line Items]
Debt instrument, amount							$ 28,200,000
ECP Holdings Loan | Term Loan
Debt Instrument [Line Items]
Debt instrument, amount							$ 6,800,000

LIABILITY MANAGEMENT TRANSACT_3

LIABILITY MANAGEMENT TRANSACTIONS - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 17, 2020	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Early extinguishment of debt		$ 306,500
Gain (loss) on early extinguishment of debt		(3,523)	$ 203,062
Open Market Repurchases | Liability Management Transactions
Debt Instrument [Line Items]
Cash consideration paid			150,300
Gain (loss) on early extinguishment of debt			86,400
Open Market Repurchases | Liability Management Transactions | 2022 Senior Notes
Debt Instrument [Line Items]
Senior Notes repurchased			32,400
Open Market Repurchases | Liability Management Transactions | 2025 Senior Notes
Debt Instrument [Line Items]
Senior Notes repurchased			201,800
Tender Offers | Liability Management Transactions
Debt Instrument [Line Items]
Cash consideration paid				$ 48,700
Gain (loss) on early extinguishment of debt			$ 23,300
Tender Offers | Liability Management Transactions | 2022 Senior Notes
Debt Instrument [Line Items]
Senior Notes repurchased				33,500
Tender Offers | Liability Management Transactions | 2025 Senior Notes
Debt Instrument [Line Items]
Senior Notes repurchased				$ 38,700
SMPH Term Loan Restructuring | Liability Management Transactions
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt	$ 94,000
Extinguishment of debt, gain (loss) (in dollars per share)	$ 26.15
Open Market Repurchases And Tender Offer Repurchase | Liability Management Transactions
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt		$ 203,100

LIABILITY MANAGEMENT TRANSACT_4

LIABILITY MANAGEMENT TRANSACTIONS - Schedule of Extinguishment of Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		$ 212,220
Debt issue costs		(5,245)
Transaction costs		(3,913)
Gain (loss) on debt extinguishment	$ (3,523)	203,062
ECP Loan Repayment
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		0
Debt issue costs		(361)
Transaction costs		(249)
Gain (loss) on debt extinguishment		(610)
T L Restructuring
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		99,175
Debt issue costs		(2,724)
Transaction costs		(2,520)
Gain (loss) on debt extinguishment		93,931
Senior Notes Due 2023 | Open Market Repurchases
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		11,554
Debt issue costs		(143)
Transaction costs		(105)
Gain (loss) on debt extinguishment		11,306
Senior Notes Due 2023 | Tender Offers
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		9,223
Debt issue costs		(125)
Transaction costs		(467)
Gain (loss) on debt extinguishment		8,631
2026 Secured Notes | Open Market Repurchases
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		76,789
Debt issue costs		(1,541)
Transaction costs		(105)
Gain (loss) on debt extinguishment		75,143
2026 Secured Notes | Tender Offers
Extinguishment of Debt [Line Items]
Gain on Repurchases of Senior Notes and TL Restructuring		15,479
Debt issue costs		(351)
Transaction costs		(467)
Gain (loss) on debt extinguishment		$ 14,661

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Rollforward of Environmental Matters (Details) - Meadowlark Midstream Gathering System - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accrual for Environmental Loss Contingencies [Roll Forward]
Accrued environmental remediation, beginning balance	$ 2,929	$ 4,651
Payments made	(1,972)	(1,722)
Additional accruals	4,649
Accrued environmental remediation, ending balance	$ 5,606	$ 2,929

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2021
Loss Contingencies [Line Items]
Legal fines and other fees			$ 36,300
2015 Blacktail Release
Loss Contingencies [Line Items]
Loss contingency in period		$ 17,000
Increase in loss contingency accrual	$ 19,300
Loss contingency accrual			$ 33,200
Unpaid penalties and fines, fixed rate (as a percent)			3.25%
Expected payment			$ 5,600
Natural Resource Damages To Federal and State Governments | 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees			$ 1,250
Penalties and fines, payment period			5 years
Damages Payable To Federal Government over Five Years | 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees			$ 25,000
Damages Payable To State Governments Over Six Years | 2015 Blacktail Release
Loss Contingencies [Line Items]
Legal fines and other fees			$ 10,000
Penalties and fines, payment period			6 years

FINANCIAL INSTRUMENTS - Narrati

FINANCIAL INSTRUMENTS - Narrative (Details)	12 Months Ended
	Dec. 31, 2021USD ($)customer	Dec. 31, 2020	Mar. 08, 2021USD ($)
CONCENTRATIONS OF RISK
Number of top customers | customer	5
Interest Rate Swap
CONCENTRATIONS OF RISK
Derivative instrument, notional amount			$ 144,000,000
Fair value of interest rate swap	$ 800,000
Five Largest Customers | Accounts receivable | Customer Concentration Risk
CONCENTRATIONS OF RISK
Concentration risk, percentage	38.00%	51.00%

FINANCIAL INSTRUMENTS - Fair va

FINANCIAL INSTRUMENTS - Fair value of Debt Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Carrying Value (1) | 2022 Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 0	$ 234,047
Carrying Value (1) | 2025 Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	259,463	259,463
Carrying Value (1) | 2026 Secured Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	700,000	0
Fair Value | 2022 Senior Notes | Estimated fair value (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	215,713
Fair Value | 2025 Senior Notes | Estimated fair value (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	234,814	168,002
Fair Value | 2026 Secured Notes | Estimated fair value (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 718,083	$ 0

PARTNERS' CAPITAL AND MEZZANI_3

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Partners' Capital and Schedule of Units (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	May 28, 2020
Energy Capital Partners | Common units
Rollforwards of the number of partner units
Cash payments to ECP		$ 35
Valuation of warrants			$ 2.3
Fair value issuance of warrants		0.7
Advisory fees and other direct costs		$ 6.8
Common Units
Rollforwards of the number of partner units
Beginning balance (in shares)	6,110,092	3,021,258
GP Buy-In Transaction (in shares)	538,715	132,687
Common units issued for SMLP LTIP, net (in shares)	106,580	95,987
TL Restructuring (in shares)		2,306,972
Series A Preferred Unit Exchange Offer, net of shares withheld for taxes (in shares)		817,845
Other (in shares)		717
ECP Warrant Exercise (in shares)	414,447
Ending balance (in shares)	7,169,834	6,110,092
Series A Preferred Units
Rollforwards of the number of partner units
Beginning balance (in shares)	162,109	300,000
Series A Preferred Unit Tender (in shares)		(75,075)
Preferred Unit Exchange Offer (in shares)	(18,662)	(62,816)
Ending balance (in shares)	143,447	162,109

PARTNERS' CAPITAL AND MEZZANI_4

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	May 28, 2020	May 27, 2020	Jan. 29, 2020	Jan. 21, 2020	Dec. 31, 2020	Nov. 30, 2017	Dec. 31, 2021	Dec. 31, 2020	Aug. 05, 2021	Apr. 30, 2021	Jul. 31, 2020
Partners Capital [Line Items]
Gain (loss) on warrant exercise							$ 13.6
Maximum period following end of quarter to distribute all available cash							45 days
Per-unit annual distributions to unitholders (in dollars per unit)			$ 0.125
Cash paid to unit holders			$ 11.7
Series A Preferred Units
Partners Capital [Line Items]
Preferred units issued (in shares)					50,000,000	300,000		50,000,000		18,662
Interest in partnership per unit (in dollars per share)						$ 1,000
Distribution rate (as a percent)						9.50%	7.00%
Liquidation preference per unit (in dollars per share)						$ 1,000	$ 1,000
Dividends payable							$ 29.9
Series A preferred per unit, price (in dollars per unit)					$ 1,000			$ 1,000
Proceeds from issuance of common limited partners units								$ 48.7
Redemption amount							$ 114.3
Paid-in-kind | Series A Preferred Units
Partners Capital [Line Items]
Distribution percentage of subsidiary unit				7.00%
Distribution percentage of liquidation preference rate of undrawn commitment units				1.00%
LIBOR | Series A Preferred Units
Partners Capital [Line Items]
Basis spread on variable rate (as a percent)						7.43%
Series A Preferred Units | Preferred Stock Exchange Offer
Partners Capital [Line Items]
Preferred units issued (in shares)											62,816
Common units
Partners Capital [Line Items]
Common units, issued (in shares)									414,447
Common units | GP Buy-In
Partners Capital [Line Items]
Number of common units purchased (in shares)		8,059,609
Common units | ECP Holdings Warrant | GP Buy-In
Partners Capital [Line Items]
Number of common units purchased (in shares)		1,940,391
Common units | Energy Capital Partners
Partners Capital [Line Items]
Exercise price of warrants (in dollars per share)	$ 15.35
Valuation of warrants	$ 2.3
Common units | Energy Capital Partners | SMLP Common Units
Partners Capital [Line Items]
Number of common units purchased (in shares)	537,307
Common units | Energy Capital Partners | ECP Holdings Warrant | SMLP Common Units
Partners Capital [Line Items]
Number of common units purchased (in shares)	129,360
Series A Preferred Units | Tender offer
Partners Capital [Line Items]
Number of shares purchased					75,075
Purchase price per share (in dollars per share)					$ 333
Number of shares purchased, value					$ 25
Subsidiary Series A Preferred Units
Partners Capital [Line Items]
Preferred units issued (in shares)					85,308,000		91,439,000	85,308,000
Preferred units issued during period (in shares)							6,131,000	5,251,000
Subsidiary Series A preferred unitholders, outstanding (in shares)					85,308,000		91,439,000	85,308,000

PARTNERS' CAPITAL AND MEZZANI_5

PARTNERS' CAPITAL AND MEZZANINE CAPITAL - Change in Subsidiary Series A Preferred Unit Balance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Partners Capital [Line Items]
Issuance costs	$ (3,900)
Series A Preferred Units
Partners Capital [Line Items]
Beginning Balance (in shares)	89,658	$ 27,450
New issuances		50,000
PIK distributions	6,131	5,251
Issuance costs		(1,290)
Redemption accretion	10,536	8,247
Ending Balance (in shares)	$ 106,325	$ 89,658

EARNINGS PER UNIT (Details)

EARNINGS PER UNIT (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ (19,949)	$ 189,078
Net loss attributable to noncontrolling interest	0	3,274
Net income (loss) attributable to Summit Midstream Partners, LP	(36,616)	178,854
Add: deemed capital contribution	$ 8,326	$ 110,669
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 (in shares)	203	240
Series A Preferred Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners	$ (15,998)	$ (26,529)
Series A Preferred Units | Subsidiaries
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners	(16,667)	(13,498)
Common units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) attributable to limited partners	$ (44,288)	$ 262,994
Weighted-average common units outstanding – basic (in shares)	6,741,000	3,592,000
Effect of nonvested phantom units (in shares)	0	102,000
Weighted-average common units outstanding – diluted (in shares)	6,741,000	3,694,000
Common unit - basic (in dollars per share)	$ (6.57)	$ 73.22
Common unit - diluted (in dollars per share)	$ (6.57)	$ 71.19

SUPPLEMENTAL CASH FLOW INFORM_3

SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Supplemental cash flow information:
Cash interest paid	$ 57,655	$ 79,450
Cash paid for taxes	191	190
Noncash investing and financing activities:
Capital expenditures in trade accounts payable (period-end accruals)	5,692	6,154
Warrant issuance for GP Buy-In Transaction	0	2,300
Right-of-use assets relating to ASC Topic 842	0	3,685
Fair value of SMLP equity for TL Restructuring	0	30,521
Exercise of ECP Warrants	15,542	0
Series A Preferred Units
Noncash investing and financing activities:
Accretion of Subsidiary Series A Preferred Units	$ 10,536	$ 8,247

UNIT-BASED AND NONCASH COMPEN_3

UNIT-BASED AND NONCASH COMPENSATION - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)director$ / sharesshares	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining vesting period	1 year 3 months 18 days
SMLP LTIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved for issuance (in shares)	1,000,000
Units remaining available (in shares)	300,000
Unrecognized unit-based compensation | $	$ 2.6
SMLP LTIP | Phantom Share Units And Associated Distribution Equivalent Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (in shares)	159,239
Granted (in dollars per unit) | $ / shares	$ 20.65
Vesting period	3 years
SMLP LTIP | Common units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common units issued (in shares)	40,002
Number of directors | director	6
Grant date fair value (in dollars per share) | $ / shares	$ 28.99
SMLP LTIP | Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (in shares)	199,241	345,997
Granted (in dollars per unit) | $ / shares	$ 22.33	$ 9.20

UNIT-BASED AND NONCASH COMPEN_4

UNIT-BASED AND NONCASH COMPENSATION - SMLP Long-Term Incentive Plan (Details) - SMLP LTIP - Phantom Units - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Units
Beginning balance (in shares)	291,691	140,400
Granted (in shares)	199,241	345,997
Vested (in shares)	(143,768)	(193,349)
Forfeited (in shares)	(13,385)	(1,357)
Ending balance (in shares)	333,779	291,691
Weighted-average grant date fair value
Beginning balance (in dollars per unit)	$ 26.57	$ 115.35
Granted (in dollars per unit)	22.33	9.20
Vested (in dollars per unit)	30.66	54.07
Forfeited (in dollars per unit)	38.85	119.24
Ending balance (in dollars per unit)	$ 21.78	$ 26.57

UNIT-BASED AND NONCASH COMPEN_5

UNIT-BASED AND NONCASH COMPENSATION - Schedule of Intrinsic Values (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
SMLP LTIP | Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of vested LTIP awards	$ 4,407	$ 2,602

UNIT-BASED AND NONCASH COMPEN_6

UNIT-BASED AND NONCASH COMPENSATION - SMP Net Profits Interests (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SMLP LTIP unit-based compensation	$ 4,744	$ 8,111
SMLP LTIP | General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SMLP LTIP unit-based compensation	$ 4,744	$ 8,111

LEASES - Narrative (Details)

LEASES - Narrative (Details)	12 Months Ended
	Dec. 31, 2021
Loss Contingencies [Line Items]
Finance leases, term of contract	3 years
Revolving credit facility
Loss Contingencies [Line Items]
Percentage of operating lease incremental borrowing rate	3.38%
Minimum | Office Space
Loss Contingencies [Line Items]
Operating leases, term of contract	3 years
Minimum | Equipment
Loss Contingencies [Line Items]
Operating leases, term of contract	3 years
Maximum | Office Space
Loss Contingencies [Line Items]
Operating leases, term of contract	10 years
Maximum | Equipment
Loss Contingencies [Line Items]
Operating leases, term of contract	4 years

LEASES - Schedule of Right of U

LEASES - Schedule of Right of Use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
ROU assets
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other noncurrent assets	Other noncurrent assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other noncurrent assets	Other noncurrent assets
Operating	$ 2,515	$ 3,736
Finance	792	1,748
Total	$ 3,307	$ 5,484
Lease liabilities, current
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities
Operating	$ 1,213	$ 2,298
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Finance	$ 167	$ 618
Total	$ 1,380	$ 2,916
Lease liabilities, noncurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other noncurrent liabilities	Other noncurrent liabilities
Operating	$ 2,272	$ 3,182
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other noncurrent liabilities	Other noncurrent liabilities
Finance	$ 122	$ 154
Total	$ 2,394	$ 3,336

LEASES - Schedule of Lease Cost

LEASES - Schedule of Lease Cost and Other Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lease cost
Amortization of ROU assets (included in depreciation and amortization)	$ 1,026	$ 1,274
Interest on lease liabilities (included in interest expense)	20	52
Operating lease cost (included in general and administrative expense)	1,722	2,644
Total lease cost	2,768	3,970
Other information
Operating cash outflows from operating leases	1,407	1,472
Operating cash outflows from finance leases	20	52
Financing cash outflows from finance leases	634	1,150
ROU assets obtained in exchange for new operating lease liabilities	0	3,552
ROU assets obtained in exchange for new finance lease liabilities	$ 94	$ 133
Weighted-average remaining lease term (years) - operating leases	5 years 1 month 6 days	4 years 10 months 24 days
Weighted-average remaining lease term (years) - finance leases	1 year 1 month 6 days	1 year 4 months 24 days
Weighted-average discount rate - operating leases (as a percent)	5.00%	5.00%
Weighted-average discount rate - finance leases (as a percent)	4.00%	4.00%

LEASES - Lease Expense (Details

LEASES - Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Lease expense	$ 2,479	$ 3,436

LEASES - Future Minimum Lease P

LEASES - Future Minimum Lease Payments Due and Future Minimum Rentals to be Received under Noncancelable Leases (Details) $ in Thousands	Dec. 31, 2021USD ($)
Operating
2022	$ 1,173
2023	854
2024	573
2025	464
2026	156
2027	160
Thereafter	418
Total future minimum lease payments	3,798
Finance
2022	173
2023	88
2024	38
2025	0
2026	0
2027	0
Thereafter	0
Total future minimum lease payments	$ 299

RESTRUCTURING - Narrative (Deta

RESTRUCTURING - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0.9	$ 5.6
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 3.5

RESTRUCTURING - Restructuring a

RESTRUCTURING - Restructuring and related costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Severance Charges	$ 810	$ 7,750
Other Restructuring Charges	104	1,349
Total Severance and Other	914	9,099
Restructuring Reserve [Roll Forward]
Accrued, Beginning Balance	3,548	2,816
Charges Incurred	914	9,099
Cash Payments	(4,462)	(8,367)
Accrued, Ending Balance	0	3,548
Employee-related costs
Restructuring Reserve [Roll Forward]
Accrued, Beginning Balance	3,548	2,816
Charges Incurred	810	7,750
Cash Payments	(4,358)	(7,018)
Accrued, Ending Balance	0	3,548
Other
Restructuring Reserve [Roll Forward]
Accrued, Beginning Balance	0	0
Charges Incurred	104	1,349
Cash Payments	(104)	(1,349)
Accrued, Ending Balance	0	0
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance Charges	810	5,591
Other Restructuring Charges	104	56
Total Severance and Other	914	5,647
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance Charges	0	2,159
Other Restructuring Charges	0	1,293
Total Severance and Other	$ 0	$ 3,452

SEGMENT INFORMATION - Assets, R

SEGMENT INFORMATION - Assets, Revenues, Depreciation and Amortization, and Capital Expenditures by Reportable Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Assets	$ 2,522,462	$ 2,499,817
Total revenues	400,618	383,473
Depreciation and amortization	119,995	119,070
Capital expenditures	25,030	43,128
Reportable Segments
Segment Reporting Information [Line Items]
Assets	2,513,633	2,487,397
Total revenues	400,578	383,473
Depreciation and amortization	117,331	115,718
Capital expenditures	24,499	39,515
Reportable Segments | Northeast
Segment Reporting Information [Line Items]
Assets	623,224	645,754
Total revenues	62,567	62,250
Depreciation and amortization	17,054	16,891
Capital expenditures	11,237	7,657
Reportable Segments | Rockies
Segment Reporting Information [Line Items]
Assets	592,148	625,793
Total revenues	145,087	120,765
Depreciation and amortization	29,513	32,057
Capital expenditures	9,875	21,596
Reportable Segments | Permian
Segment Reporting Information [Line Items]
Assets	458,988	299,421
Total revenues	40,848	32,109
Depreciation and amortization	5,858	5,455
Capital expenditures	2,042	7,014
Reportable Segments | Piceance
Segment Reporting Information [Line Items]
Assets	524,218	579,800
Total revenues	105,485	113,890
Depreciation and amortization	48,773	45,203
Capital expenditures	579	1,370
Reportable Segments | Barnett
Segment Reporting Information [Line Items]
Assets	315,055	336,629
Total revenues	46,591	54,459
Depreciation and amortization	16,133	16,112
Capital expenditures	766	1,878
Corporate and Other
Segment Reporting Information [Line Items]
Assets	8,829	12,420
Total revenues	40	0
Depreciation and amortization	2,664	3,352
Capital expenditures	$ 531	$ 3,613

SEGMENT INFORMATION - Concentra

SEGMENT INFORMATION - Concentration Risk (Details) - Sales Revenue, Net - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Counterparty A - Piceance Basin
Segment Reporting Information [Line Items]
Concentration risk, percentage	12.00%	13.00%
Counterparty C - Utica Shale
Segment Reporting Information [Line Items]
Concentration risk, percentage		5.00%
Counterparty C - Permian Basin
Segment Reporting Information [Line Items]
Concentration risk, percentage		5.00%
Counterparty C - Barnett Shale
Segment Reporting Information [Line Items]
Concentration risk, percentage		1.00%

SEGMENT INFORMATION - Adjusted

SEGMENT INFORMATION - Adjusted EBITDA by Reportable Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 267,278	$ 284,020
Northeast
Segment Reporting Information [Line Items]
Adjusted EBITDA	83,287	85,854
Rockies
Segment Reporting Information [Line Items]
Adjusted EBITDA	64,517	71,509
Permian
Segment Reporting Information [Line Items]
Adjusted EBITDA	6,614	5,744
Piceance
Segment Reporting Information [Line Items]
Adjusted EBITDA	76,131	88,820
Barnett
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 36,729	$ 32,093

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Net Income (Loss) to Adjusted EBITDA (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting [Abstract]
Income (loss) before income taxes and equity method investment income	$ (28,156)	$ 177,661
Add:
Corporate and Other expense	68,783	60,903
Interest expense	66,156	78,894
Gain on early extinguishment of debt	3,523	(203,062)
Depreciation and amortization	119,995	119,070
Proportional adjusted EBITDA for equity method investees	29,022	31,056
Adjustments related to capital reimbursement activity	(6,571)	(1,395)
Unit-based and noncash compensation	4,744	8,111
Gain on asset sales, net	(369)	(307)
Long-lived asset impairment	10,151	13,089
Total of reportable segments' measures of profit	$ 267,278	$ 284,020

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in Millions	Jan. 12, 2022	Jan. 31, 2022	Nov. 30, 2017
Series A Preferred Units | LIBOR
Subsequent Event [Line Items]
Basis spread on variable rate (as a percent)			7.43%
Subsequent Event | Permian Term Loan Facility
Subsequent Event [Line Items]
Term loan facility		$ 160
Amortization period of debt instrument		10 years
Subsequent Event | Permian Term Loan Facility | LIBOR
Subsequent Event [Line Items]
Basis spread on variable rate (as a percent)		2.375%
Subsequent Event | Series A Preferred Units
Subsequent Event [Line Items]
Shares exchanged	77,939
Subsequent Event | Common Units
Subsequent Event [Line Items]
Shares issued (in shares)	2,853,875