UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	Partners' Capital	Partners' Capital Series A Preferred Units	Noncontrolling Interest Series A Preferred Units	Noncontrolling Interest Common Noncontrolling Interest	[1]
Beginning balance at Dec. 31, 2018	$ 1,391,567	$ 543,479		$ 293,616	$ 554,472
Net income (loss)	(40,280)	(21,835)		7,125	(25,570)
Net cash distributions to SMLP unitholders	(27,374)				(27,374)
Unit-based compensation	2,526				2,526
Effect of common unit issuances under SMLP LTIP		(2,387)			2,387
Tax withholdings and associated payments on vested SMLP LTIP awards	(2,524)				(2,524)
Conversion of noncontrolling interest related to cancellation of subsidiary incentive distribution rights		48,203			(48,203)
Ending balance at Mar. 31, 2019	1,323,915	567,460		300,741	455,714
Net income (loss)	3,028	(2,756)		7,125	(1,341)
Net cash distributions to SMLP unitholders	(28,076)			(14,250)	(13,826)
Net cash distributions to Energy Capital Partners	(68,984)	(68,984)
Unit-based compensation	1,393				1,393
Effect of common unit issuances under SMLP LTIP		(40)			40
Tax withholdings and associated payments on vested SMLP LTIP awards	(93)				(93)
Ending balance at Jun. 30, 2019	1,231,183	495,680		293,616	441,887
Net income (loss)	(11,129)	(7,914)		7,125	(10,340)
Net cash distributions to SMLP unitholders	(13,829)				(13,829)
Unit-based compensation	1,451				1,451
Effect of common unit issuances under SMLP LTIP		(173)			173
Tax withholdings and associated payments on vested SMLP LTIP awards	55				55
Ending balance at Sep. 30, 2019	1,207,731	487,593		300,741	419,397
Beginning balance at Dec. 31, 2019	785,236	305,550		293,616	186,070
Net income (loss)	2,817	(2,427)		7,125	(1,881)
Net cash distributions to SMLP unitholders	(6,037)				(6,037)
Unit-based compensation	2,723				2,723
Effect of common unit issuances under SMLP LTIP		(2,322)			2,322
Tax withholdings and associated payments on vested SMLP LTIP awards	(984)				(984)
Ending balance at Mar. 31, 2020	783,755	300,801		300,741	182,213
Beginning balance at Dec. 31, 2019	785,236	305,550		293,616	186,070
Conversion of noncontrolling interest related to cancellation of subsidiary incentive distribution rights	54,945
Ending balance at Sep. 30, 2020	816,635	567,284	$ 249,351
Beginning balance at Mar. 31, 2020	783,755	300,801		300,741	182,213
Net income (loss)	55,324	49,592	2,375	4,750	(1,393)
Unit-based compensation	1,846	515			1,331
Tax withholdings and associated payments on vested SMLP LTIP awards	(62)	(28)			(34)
GP Buy-In Transaction assumption of noncontrolling interest in SMLP		182,117	305,491	$ (305,491)	$ (182,117)
Repurchase of common units under GP Buy-In Transaction	(44,078)	(44,078)
Other	(61)	(61)
Ending balance at Jun. 30, 2020	796,724	488,858	307,866
Net income (loss)	18,331	11,850	6,481
Unit-based compensation	1,622	1,622
Tax withholdings and associated payments on vested SMLP LTIP awards	(117)	(117)
Tax withholdings on Series A Preferred Unit Exchange	(237)	(237)
Conversion of Series A Preferred Units to SMLP common units inclusive of a $54.9 million deemed contribution to common unit holders (Note 10)		64,996	(64,996)
Other	312	312
Conversion of noncontrolling interest related to cancellation of subsidiary incentive distribution rights	54,945
Ending balance at Sep. 30, 2020	$ 816,635	$ 567,284	$ 249,351

[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.