CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL - USD ($) $ in Thousands	Total	Class B membership interest	Noncontrolling interest	Noncontrolling interest Class B membership interest	Summit Investments' equity in contributed subsidiaries	Summit Investments' equity in contributed subsidiaries Class B membership interest	Common	Common Class B membership interest	Limited partners, Subordinated	Limited partners, Subordinated Class B membership interest	Limited partners, Series A Preferred Units	General Partner	General Partner Class B membership interest	At Market Program	At Market Program Noncontrolling interest	At Market Program Common	At Market Program Limited partners, Series A Preferred Units	At Market Program General Partner
Beginning balance at Dec. 31, 2014	$ 1,830,678				$ 863,789		$ 649,060		$ 293,153			$ 24,676
Net (loss) income	(222,228)				(30,016)		(123,817)		(71,793)			3,398
Distributions to unitholders	(152,074)						(86,880)		(55,410)			(9,784)
Unit-based compensation	6,174	$ 843				$ 843	6,174
Tax withholdings on vested SMLP LTIP awards	(1,616)						(1,616)
Issuance of common/preferred units, net of offering costs	221,977						221,977
Contribution from General Partner	4,737											4,737
Purchase of contributed Subsidiaries	(285,677)				(285,677)
Excess of acquired carrying value over consideration paid					(130,367)		80,079		47,681			2,607
Cash advance from Summit Investments to contributed subsidiaries, net	320,527				320,527
Expenses paid by Summit Investments on behalf of contributed subsidiaries	22,879				22,879
Capitalized interest allocated to contributed subsidiaries from Summit Investments	1,079				1,079
Ending balance at Dec. 31, 2015	1,747,299		$ 0		763,057		744,977		213,631			25,634
Net (loss) income	(38,187)		(14)		2,745		(49,219)		1,040			7,261
Distributions to unitholders	(167,504)		0		0		(142,214)		(14,034)			(11,256)
Unit-based compensation	7,550	$ 435	0	$ 0	0	$ 130	7,550	$ 305	0	$ 0		0	$ 0
Tax withholdings on vested SMLP LTIP awards	(1,181)		0		0		(1,181)		0			0
Issuance of common/preferred units, net of offering costs	125,233		0		0		125,233		0			0
Contribution from General Partner	2,702		0		0		0		0			2,702
Subordinated units conversion	0		0		0		200,637		(200,637)			0
Purchase of contributed Subsidiaries	(866,858)		0		(866,858)		0		0			0
Establishment of noncontrolling interest	0		11,261		(11,261)		0		0			0
Distribution of debt related to Carve-Out Financial Statements of Summit Investments	342,926		0		342,926		0		0			0
Excess of acquired carrying value over consideration paid	0		0		(247,997)		243,044		0			4,953
Cash advance from Summit Investments to contributed subsidiaries, net	12,214		0		12,214		0		0			0
Expenses paid by Summit Investments on behalf of contributed subsidiaries	4,821		0		4,821		0		0			0
Capitalized interest allocated to contributed subsidiaries from Summit Investments	223		0		223		0		0			0
Ending balance at Dec. 31, 2016	1,169,673		11,247		$ 0		1,129,132		$ 0		$ 0	29,294
Net (loss) income	86,050		363				71,922				3,563	10,202
Distributions to unitholders	(181,478)		0				(167,062)				(2,375)	(12,041)
Unit-based compensation	7,878		0				7,878				0	0
Tax withholdings on vested SMLP LTIP awards	(2,236)		0				(2,236)				0	0
Issuance of common/preferred units, net of offering costs	293,238		0				0				293,238	0		$ 17,078	$ 0	$ 17,078	$ 0	$ 0
Contribution from General Partner	465		0				0				0	465
Purchase of noncontrolling interest	(797)		(797)				0				0	0
Other	(202)		0				(202)				0	0
Ending balance at Dec. 31, 2017	$ 1,389,669		$ 10,813				$ 1,056,510				$ 294,426	$ 27,920