CONDENSED CONSOLIDATING FINANCIAL INFORMATION - Condensed Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 8,212		$ 1,430	$ 2,588	$ 7,428
Accounts receivable	80,166		72,301
Other current assets	2,594		4,327
Due from affiliate	0		0
Total current assets	90,972		78,058
Property, plant and equipment, net	1,887,759	$ 1,828,252	1,795,129
Intangible assets, net	286,665		301,345
Goodwill	16,211		16,211
Investment in equity method investees	670,827		690,485
Other noncurrent assets	13,144		13,565
Investment in subsidiaries	0		0
Total assets	2,965,578		2,894,793
Liabilities and Partners' Capital
Trade accounts payable	21,698		16,375
Accrued expenses	19,433		12,499
Due to affiliate	91		1,088
Deferred revenue	10,778	10,088	4,000
Ad valorem taxes payable	6,504		8,329
Accrued interest	12,259		12,310
Accrued environmental remediation	3,522		3,130
Other current liabilities	7,412		11,258
Total current liabilities	81,697		68,989
Long-term debt	1,147,005		1,051,192
Deferred Purchase Price Obligation	453,922		362,959
Noncurrent deferred revenue	38,119	$ 35,528	12,707
Noncurrent accrued environmental remediation	1,617		2,214
Other noncurrent liabilities	6,410		7,063
Total liabilities	1,728,770		1,505,124
Total partners' capital	1,236,808		1,389,669	1,110,899	1,169,673
Total liabilities and partners' capital	2,965,578		2,894,793
Consolidating adjustments
Assets
Cash and cash equivalents	0		0	0	0
Accounts receivable	0		0
Other current assets	0		0
Due from affiliate	(559,248)		(515,097)
Total current assets	(559,248)		(515,097)
Property, plant and equipment, net	0		0
Intangible assets, net	0		0
Goodwill	0		0
Investment in equity method investees	0		0
Other noncurrent assets	0		0
Investment in subsidiaries	(5,458,867)		(5,344,164)
Total assets	(6,018,115)		(5,859,261)
Liabilities and Partners' Capital
Trade accounts payable	0		0
Accrued expenses	0		0
Due to affiliate	(559,248)		(515,097)
Deferred revenue	0		0
Ad valorem taxes payable	0		0
Accrued interest	0		0
Accrued environmental remediation	0		0
Other current liabilities	0		0
Total current liabilities	(559,248)		(515,097)
Long-term debt	0		0
Deferred Purchase Price Obligation	0		0
Noncurrent deferred revenue	0		0
Noncurrent accrued environmental remediation	0		0
Other noncurrent liabilities	0		0
Total liabilities	(559,248)		(515,097)
Total partners' capital	(5,458,867)		(5,344,164)
Total liabilities and partners' capital	(6,018,115)		(5,859,261)
Summit Midstream Partners, LP | Reportable Legal Entities
Assets
Cash and cash equivalents	2,616		126	228	698
Accounts receivable	22		22
Other current assets	1,057		1,188
Due from affiliate	0		0
Total current assets	3,695		1,336
Property, plant and equipment, net	4,314		4,206
Intangible assets, net	0		0
Goodwill	0		0
Investment in equity method investees	0		0
Other noncurrent assets	3,288		2,547
Investment in subsidiaries	2,062,096		2,019,700
Total assets	2,073,393		2,027,789
Liabilities and Partners' Capital
Trade accounts payable	141		209
Accrued expenses	803		928
Due to affiliate	374,074		263,935
Deferred revenue	0		0
Ad valorem taxes payable	9		0
Accrued interest	0		0
Accrued environmental remediation	0		0
Other current liabilities	3,477		6,395
Total current liabilities	378,504		271,467
Long-term debt	0		0
Deferred Purchase Price Obligation	453,922		362,959
Noncurrent deferred revenue	0		0
Noncurrent accrued environmental remediation	0		0
Other noncurrent liabilities	4,159		3,694
Total liabilities	836,585		638,120
Total partners' capital	1,236,808		1,389,669
Total liabilities and partners' capital	2,073,393		2,027,789
Co-Issuers | Reportable Legal Entities
Assets
Cash and cash equivalents	92		75	79	51
Accounts receivable	0		0
Other current assets	0		0
Due from affiliate	0		0
Total current assets	92		75
Property, plant and equipment, net	0		0
Intangible assets, net	0		0
Goodwill	0		0
Investment in equity method investees	0		0
Other noncurrent assets	9,762		10,913
Investment in subsidiaries	3,396,771		3,324,464
Total assets	3,406,625		3,335,452
Liabilities and Partners' Capital
Trade accounts payable	0		0
Accrued expenses	0		0
Due to affiliate	185,265		252,250
Deferred revenue	0		0
Ad valorem taxes payable	0		0
Accrued interest	12,259		12,310
Accrued environmental remediation	0		0
Other current liabilities	0		0
Total current liabilities	197,524		264,560
Long-term debt	1,147,005		1,051,192
Deferred Purchase Price Obligation	0		0
Noncurrent deferred revenue	0		0
Noncurrent accrued environmental remediation	0		0
Other noncurrent liabilities	0		0
Total liabilities	1,344,529		1,315,752
Total partners' capital	2,062,096		2,019,700
Total liabilities and partners' capital	3,406,625		3,335,452
Guarantor Subsidiaries | Reportable Legal Entities
Assets
Cash and cash equivalents	4,998		1,138	2,064	5,768
Accounts receivable	68,274		65,842
Other current assets	1,273		2,697
Due from affiliate	507,396		493,067
Total current assets	581,941		562,744
Property, plant and equipment, net	1,537,468		1,442,333
Intangible assets, net	263,416		278,958
Goodwill	16,211		16,211
Investment in equity method investees	0		0
Other noncurrent assets	94		105
Investment in subsidiaries	0		0
Total assets	2,399,130		2,300,351
Liabilities and Partners' Capital
Trade accounts payable	18,280		11,283
Accrued expenses	17,030		10,592
Due to affiliate	0		0
Deferred revenue	10,341		4,000
Ad valorem taxes payable	6,224		7,809
Accrued interest	0		0
Accrued environmental remediation	0		0
Other current liabilities	3,573		4,385
Total current liabilities	55,448		38,069
Long-term debt	0		0
Deferred Purchase Price Obligation	0		0
Noncurrent deferred revenue	36,416		12,707
Noncurrent accrued environmental remediation	0		0
Other noncurrent liabilities	2,197		3,293
Total liabilities	94,061		54,069
Total partners' capital	2,305,069		2,246,282
Total liabilities and partners' capital	2,399,130		2,300,351
Non-Guarantor Subsidiaries | Reportable Legal Entities
Assets
Cash and cash equivalents	506		91	$ 217	$ 911
Accounts receivable	11,870		6,437
Other current assets	264		442
Due from affiliate	51,852		22,030
Total current assets	64,492		29,000
Property, plant and equipment, net	345,977		348,590
Intangible assets, net	23,249		22,387
Goodwill	0		0
Investment in equity method investees	670,827		690,485
Other noncurrent assets	0		0
Investment in subsidiaries	0		0
Total assets	1,104,545		1,090,462
Liabilities and Partners' Capital
Trade accounts payable	3,277		4,883
Accrued expenses	1,600		979
Due to affiliate	0		0
Deferred revenue	437		0
Ad valorem taxes payable	271		520
Accrued interest	0		0
Accrued environmental remediation	3,522		3,130
Other current liabilities	362		478
Total current liabilities	9,469		9,990
Long-term debt	0		0
Deferred Purchase Price Obligation	0		0
Noncurrent deferred revenue	1,703		0
Noncurrent accrued environmental remediation	1,617		2,214
Other noncurrent liabilities	54		76
Total liabilities	12,843		12,280
Total partners' capital	1,091,702		1,078,182
Total liabilities and partners' capital	$ 1,104,545		$ 1,090,462