CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net cash provided by (used in) operating activities	$ 166,492	$ 196,497
Cash flows from investing activities:
Capital expenditures	(137,033)	(86,206)
Proceeds from asset sale	496	2,300
Contributions to equity method investees	0	(21,581)
Other, net	(209)	(579)
Advances to affiliates	0	0
Net cash provided by (used in) investing activities	(136,746)	(106,066)
Cash flows from financing activities:
Distributions to unitholders		(134,066)
Borrowings under Revolving Credit Facility	202,000	177,500
Repayments under Revolving Credit Facility	(79,000)	(319,500)
Debt issuance costs	(334)	(15,891)
Payment of redemption and call premiums on senior notes	0	(17,913)
Proceeds from ATM Program common unit issuances, net of costs	0	17,251
Contribution from General Partner	0	465
Issuance of senior notes	0	500,000
Tender and redemption of senior notes	0	(300,000)
Other, net	(3,738)	(2,794)
Advances from affiliates	0	0
Net cash provided by (used in) financing activities	(30,806)	(94,948)
Net change in cash and cash equivalents	(1,060)	(4,517)
Cash and cash equivalents, beginning of period	1,430	7,428
Cash and cash equivalents, end of period	370	2,911
Consolidating adjustments
Cash flows from operating activities:
Net cash provided by (used in) operating activities	0	0
Cash flows from investing activities:
Capital expenditures	0	0
Proceeds from asset sale	0	0
Contributions to equity method investees		0
Other, net	0	0
Advances to affiliates	151,040	91,269
Net cash provided by (used in) investing activities	151,040	91,269
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	(151,040)	(91,269)
Net cash provided by (used in) financing activities	(151,040)	(91,269)
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
Summit Midstream Partners, LP | Reportable Legal Entities
Cash flows from operating activities:
Net cash provided by (used in) operating activities	3,687	5,707
Cash flows from investing activities:
Capital expenditures	(2,101)	(995)
Proceeds from asset sale	0	0
Contributions to equity method investees		0
Other, net	(209)	(579)
Advances to affiliates	0	11,768
Net cash provided by (used in) investing activities	(2,310)	10,194
Cash flows from financing activities:
Distributions to unitholders		(134,066)
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		17,251
Contribution from General Partner		465
Issuance of senior notes		0
Tender and redemption of senior notes		0
Other, net	(2,780)	(2,794)
Advances from affiliates	151,040	103,037
Net cash provided by (used in) financing activities	(1,474)	(16,107)
Net change in cash and cash equivalents	(97)	(206)
Cash and cash equivalents, beginning of period	126	698
Cash and cash equivalents, end of period	29	492
Co-Issuers | Reportable Legal Entities
Cash flows from operating activities:
Net cash provided by (used in) operating activities	(38,590)	(45,854)
Cash flows from investing activities:
Capital expenditures	0	0
Proceeds from asset sale	0	0
Contributions to equity method investees		0
Other, net	0	0
Advances to affiliates	(84,148)	21,658
Net cash provided by (used in) investing activities	(84,148)	21,658
Cash flows from financing activities:
Distributions to unitholders		0
Borrowings under Revolving Credit Facility	202,000	177,500
Repayments under Revolving Credit Facility	(79,000)	(319,500)
Debt issuance costs	(334)	(15,891)
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	122,666	24,196
Net change in cash and cash equivalents	(72)	0
Cash and cash equivalents, beginning of period	75	51
Cash and cash equivalents, end of period	3	51
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities:
Net cash provided by (used in) operating activities	148,237	176,442
Cash flows from investing activities:
Capital expenditures	(127,362)	(64,413)
Proceeds from asset sale	0	0
Contributions to equity method investees		0
Other, net	0	0
Advances to affiliates	(20,802)	(116,254)
Net cash provided by (used in) investing activities	(148,164)	(180,667)
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	(881)	0
Advances from affiliates	0	0
Net cash provided by (used in) financing activities	(881)	0
Net change in cash and cash equivalents	(808)	(4,225)
Cash and cash equivalents, beginning of period	1,138	5,768
Cash and cash equivalents, end of period	330	1,543
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities:
Net cash provided by (used in) operating activities	53,158	60,202
Cash flows from investing activities:
Capital expenditures	(7,570)	(20,798)
Proceeds from asset sale	496	2,300
Contributions to equity method investees		(21,581)
Other, net	0	0
Advances to affiliates	(46,090)	(8,441)
Net cash provided by (used in) investing activities	(53,164)	(48,520)
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	(77)	0
Advances from affiliates	0	(11,768)
Net cash provided by (used in) financing activities	(77)	(11,768)
Net change in cash and cash equivalents	(83)	(86)
Cash and cash equivalents, beginning of period	91	911
Cash and cash equivalents, end of period	8	825
Common units
Cash flows from financing activities:
Distributions to unitholders	(135,484)	(134,066)
Common units | Consolidating adjustments
Cash flows from financing activities:
Distributions to unitholders	0
Common units | Summit Midstream Partners, LP | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	(135,484)
Common units | Co-Issuers | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Common units | Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Common units | Non-Guarantor Subsidiaries | Reportable Legal Entities
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
Series A Preferred Units | Summit Midstream Partners, LP | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	(14,250)
Series A Preferred Units | Co-Issuers | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Series A Preferred Units | Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	0
Series A Preferred Units | Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from financing activities:
Distributions to unitholders	$ 0