UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 100,187	$ 127,479	$ 331,281	$ 372,982
Costs and expenses:
Cost of natural gas and NGLs	$ 7,472	$ 26,879	$ 50,802	$ 71,549
Type of Cost, Good or Service [Extensible List]	us-gaap:OilAndGasPurchasedMember	us-gaap:OilAndGasPurchasedMember	us-gaap:OilAndGasPurchasedMember	us-gaap:OilAndGasPurchasedMember
Operation and maintenance	$ 26,231	$ 24,382	$ 74,171	$ 73,452
General and administrative	9,949	11,740	37,444	39,666
Depreciation and amortization	27,406	26,743	81,933	80,204
Transaction costs	129	0	1,079	0
(Gain) loss on asset sales, net	(347)	6	(1,595)	(6)
Long-lived asset impairment	0	1,540	45,021	2,127
Goodwill impairment	16,211	0	16,211	0
Total costs and expenses	87,051	91,290	305,066	266,992
Other income	12	58	304	78
Interest expense	(19,335)	(14,862)	(54,803)	(44,821)
Deferred Purchase Price Obligation	(3,760)	37,204	(11,899)	(53,759)
(Loss) income before income taxes and loss from equity method investees	(9,947)	58,589	(40,183)	7,488
Income tax (expense) benefit	(21)	35	(1,370)	(88)
Loss from equity method investees	(677)	(1,169)	(1,197)	(3,703)
Net (loss) income	(10,645)	57,455	(42,750)	3,697
Net income attributable to noncontrolling interest	0	25	0	168
Net (loss) income attributable to SMLP	(10,645)	57,430	(42,750)	3,529
Net income attributable to General Partner, including IDRs	0	3,279	12	6,477
Net (loss) income attributable to limited partners	(10,645)	54,151	(42,762)	(2,948)
Series A Preferred Units
Costs and expenses:
Net (loss) income attributable to limited partners	7,125	7,125	21,375	21,375
Common units
Costs and expenses:
Net (loss) income attributable to limited partners	$ (17,770)	$ 47,026	$ (64,137)	$ (24,323)
(Loss) income per limited partner unit:
Basic (in dollars per share)	$ (0.21)	$ 0.64	$ (0.80)	$ (0.33)
Diluted (in dollars per share)	$ (0.21)	$ 0.64	$ (0.80)	$ (0.33)
Weighted-average limited partner units outstanding:
Basic (shares)	82,718	73,356	80,429	73,283
Diluted (shares)	82,718	73,756	80,429	73,283
Gathering Services and Related Fees
Revenues:
Total revenues	$ 80,968	$ 86,427	$ 243,039	$ 260,373
Natural Gas, NGLs and Condensate Sales
Revenues:
Total revenues	12,219	34,017	68,438	92,025
Other Revenues
Revenues:
Total revenues	$ 7,000	$ 7,035	$ 19,804	$ 20,584