CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net cash (used in) provided by operating activities	$ 110,049	$ 121,341
Cash flows from investing activities:
Capital expenditures	(90,394)	(45,912)
Contributions to equity method investees	0	(15,649)
Proceeds from asset sale	496	0
Other, net	(306)	(521)
Advances to affiliates	0	0
Net cash provided by (used in) investing activities	(90,204)	(62,082)
Cash flows from financing activities:
Distributions to unitholders		(89,029)
Borrowings under Revolving Credit Facility	148,000	112,500
Repayments under Revolving Credit Facility	(53,000)	(269,500)
Debt issuance costs	(121)	(15,613)
Payment of redemption and call premiums on senior notes	0	(17,913)
Proceeds from ATM Program common unit issuances, net of costs	0	17,259
Contribution from General Partner	0	465
Issuance of senior notes	0	500,000
Tender and redemption of senior notes	0	(300,000)
Other, net	(3,423)	(2,268)
Advances from affiliates	0	0
Net cash provided by (used in) financing activities	(13,063)	(64,099)
Net change in cash and cash equivalents	6,782	(4,840)
Cash and cash equivalents, beginning of period	1,430	7,428
Cash and cash equivalents, end of period	8,212	2,588
Consolidating adjustments
Cash flows from operating activities:
Net cash (used in) provided by operating activities	0	0
Cash flows from investing activities:
Capital expenditures	0	0
Contributions to equity method investees		0
Proceeds from asset sale	0
Other, net	0	0
Advances to affiliates	111,134	64,706
Net cash provided by (used in) investing activities	111,134	64,706
Cash flows from financing activities:
Distributions to unitholders		0
Borrowings under Revolving Credit Facility	0	0
Repayments under Revolving Credit Facility	0	0
Debt issuance costs	0	0
Payment of redemption and call premiums on senior notes		0
Proceeds from ATM Program common unit issuances, net of costs		0
Contribution from General Partner		0
Issuance of senior notes		0
Tender and redemption of senior notes		0
Other, net	0	0
Advances from affiliates	(111,134)	(64,706)
Net cash provided by (used in) financing activities	(111,134)	(64,706)
Net change in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Common units
Cash flows from financing activities:
Distributions to unitholders	(90,269)	(89,029)
Common units | Consolidating adjustments
Cash flows from financing activities:
Distributions to unitholders	0
Series A Preferred Units
Cash flows from financing activities:
Distributions to unitholders	(14,250)	0
Series A Preferred Units | Consolidating adjustments
Cash flows from financing activities:
Distributions to unitholders	0
Summit Midstream Partners, LP | Reportable Legal Entities
Cash flows from operating activities:
Net cash (used in) provided by operating activities	(68)	424
Cash flows from investing activities:
Capital expenditures	(972)	(6,412)
Contributions to equity method investees		0
Proceeds from asset sale	0
Other, net	(306)	(521)
Advances to affiliates	0	7,635
Net cash provided by (used in) investing activities	(1,278)	702
Cash flows from financing activities:
Distributions to unitholders		(89,029)
Borrowings under Revolving Credit Facility	0	0
Repayments under Revolving Credit Facility	0	0
Debt issuance costs	0	0
Payment of redemption and call premiums on senior notes		0
Proceeds from ATM Program common unit issuances, net of costs		17,259
Contribution from General Partner		465
Issuance of senior notes		0
Tender and redemption of senior notes		0
Other, net	(2,779)	(2,632)
Advances from affiliates	111,134	72,341
Net cash provided by (used in) financing activities	3,836	(1,596)
Net change in cash and cash equivalents	2,490	(470)
Cash and cash equivalents, beginning of period	126	698
Cash and cash equivalents, end of period	2,616	228
Summit Midstream Partners, LP | Common units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	(90,269)
Summit Midstream Partners, LP | Series A Preferred Units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	(14,250)
Co-Issuers | Reportable Legal Entities
Cash flows from operating activities:
Net cash (used in) provided by operating activities	(27,877)	(32,466)
Cash flows from investing activities:
Capital expenditures	0	0
Contributions to equity method investees		0
Proceeds from asset sale	0
Other, net	0	0
Advances to affiliates	(66,985)	23,020
Net cash provided by (used in) investing activities	(66,985)	23,020
Cash flows from financing activities:
Distributions to unitholders		0
Borrowings under Revolving Credit Facility	148,000	112,500
Repayments under Revolving Credit Facility	(53,000)	(269,500)
Debt issuance costs	(121)	(15,613)
Payment of redemption and call premiums on senior notes		(17,913)
Proceeds from ATM Program common unit issuances, net of costs		0
Contribution from General Partner		0
Issuance of senior notes		500,000
Tender and redemption of senior notes		(300,000)
Other, net	0	0
Advances from affiliates	0	0
Net cash provided by (used in) financing activities	94,879	9,474
Net change in cash and cash equivalents	17	28
Cash and cash equivalents, beginning of period	75	51
Cash and cash equivalents, end of period	92	79
Co-Issuers | Common units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Co-Issuers | Series A Preferred Units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities:
Net cash (used in) provided by operating activities	103,965	114,863
Cash flows from investing activities:
Capital expenditures	(85,187)	(23,578)
Contributions to equity method investees		0
Proceeds from asset sale	0
Other, net	0	0
Advances to affiliates	(14,329)	(95,361)
Net cash provided by (used in) investing activities	(99,516)	(118,939)
Cash flows from financing activities:
Distributions to unitholders		0
Borrowings under Revolving Credit Facility	0	0
Repayments under Revolving Credit Facility	0	0
Debt issuance costs	0	0
Payment of redemption and call premiums on senior notes		0
Proceeds from ATM Program common unit issuances, net of costs		0
Contribution from General Partner		0
Issuance of senior notes		0
Tender and redemption of senior notes		0
Other, net	(589)	372
Advances from affiliates	0	0
Net cash provided by (used in) financing activities	(589)	372
Net change in cash and cash equivalents	3,860	(3,704)
Cash and cash equivalents, beginning of period	1,138	5,768
Cash and cash equivalents, end of period	4,998	2,064
Guarantor Subsidiaries | Common units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Guarantor Subsidiaries | Series A Preferred Units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities:
Net cash (used in) provided by operating activities	34,029	38,520
Cash flows from investing activities:
Capital expenditures	(4,235)	(15,922)
Contributions to equity method investees		(15,649)
Proceeds from asset sale	496
Other, net	0	0
Advances to affiliates	(29,820)	0
Net cash provided by (used in) investing activities	(33,559)	(31,571)
Cash flows from financing activities:
Distributions to unitholders		0
Borrowings under Revolving Credit Facility	0	0
Repayments under Revolving Credit Facility	0	0
Debt issuance costs	0	0
Payment of redemption and call premiums on senior notes		0
Proceeds from ATM Program common unit issuances, net of costs		0
Contribution from General Partner		0
Issuance of senior notes		0
Tender and redemption of senior notes		0
Other, net	(55)	(8)
Advances from affiliates	0	(7,635)
Net cash provided by (used in) financing activities	(55)	(7,643)
Net change in cash and cash equivalents	415	(694)
Cash and cash equivalents, beginning of period	91	911
Cash and cash equivalents, end of period	506	$ 217
Non-Guarantor Subsidiaries | Common units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Non-Guarantor Subsidiaries | Series A Preferred Units | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	$ 0