UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Total revenues	$ 99,318	$ 104,903
Costs and expenses:
Cost of natural gas and NGLs	$ 20,476	$ 8,225
Type of Cost, Good or Service [Extensible List]	us-gaap:OilAndGasPurchasedMember	us-gaap:OilAndGasPurchasedMember
Operation and maintenance	$ 16,593	$ 21,811
General and administrative	10,344	16,561
Depreciation and amortization	28,511	29,666
Transaction costs		11
(Gain) loss on asset sales, net	(136)	115
Long-lived asset impairments	1,492	3,821
Total costs and expenses	77,280	80,210
Other income (expense), net	55	(427)
Interest expense	(13,953)	(23,828)
Loss on ECP Warrants and other	(1,481)	0
Income before income taxes and equity method investment income	6,659	438
Income tax benefit	14	13
Income from equity method investees	2,315	3,311
Net income	8,988	3,762
Net income (loss) attributable to limited partners	5,056	4,698
Net loss attributable to noncontrolling interest		1,881
Net income attributable to Summit Midstream Partners, LP	5,056	4,698
Series A Preferred Units
Costs and expenses:
Net income (loss) attributable to limited partners	(4,287)	(7,125)
Series A Preferred Units | Subsidiary
Costs and expenses:
Net income (loss) attributable to limited partners	(3,932)	(945)
Common Units
Costs and expenses:
Net income (loss) attributable to limited partners	$ 769	$ (2,427)
Net income (loss) per limited partner unit:
Basic (in dollars per share)	$ 0.13	$ (0.80)
Diluted (in dollars per share)	$ 0.12	$ (0.80)
Weighted-average limited partner units outstanding:
Basic (shares)	6,125	3,021
Diluted (shares)	6,260	3,021
Gathering Services and Related Fees
Revenues:
Total revenues	$ 70,348	$ 83,792
Natural Gas, NGLs and Condensate Sales
Revenues:
Total revenues	20,763	13,780
Other Revenues
Revenues:
Total revenues	$ 8,207	$ 7,331