Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended
		Feb. 28, 2019	Mar. 31, 2019		Jun. 30, 2018	Mar. 31, 2018		Dec. 31, 2018
Acquisitions			$ 92,546
Common units outstanding			452,990,862					218,937,797
Conversion ratio per unit		1.525
Revenues and other			$ 671,883			$ 501,054	[1]
Cost of product	[2]		$ 114,063			94,318	[1]
Prior Period Adjustment [Member]
Cost of product						19,600
Prior Period Adjustment [Member] | Service Revenues - Fee Based [Member]
Revenues and other						14,300
Prior Period Adjustment [Member] | Product Sales [Member]
Revenues and other						5,300
Chipeta [Member]
Ownership interest by noncontrolling interest owner			25.00%
WES Operating [Member]
Ownership interest by noncontrolling interest owner			2.00%
Anadarko Midstream Assets [Member]
Conversion ratio per unit		1.4056
Revenues and other						51,664
Affiliates [Member]
Revenues and other	[3]		$ 378,437			285,176	[1]
Cost of product	[3]		56,172			34,819
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			326,642			222,038	[1]
Affiliates [Member] | Product Sales [Member]
Revenues and other			50,443			62,507	[1]
Affiliates [Member] | Product Sales [Member] | Kitty Draw and Third Creek Gathering Systems [Member]
Revenues and other			$ 5,500		$ (10,900)
WES Operating [Member]
Units issued			308,723
General partner units owned			0					2,583,068
Conversion of units	[4]		0
Revenues and other			$ 671,883			501,054	[1]
Cost of product	[5]		$ 114,063			94,318	[1]
WES Operating [Member] | Anadarko Midstream Assets [Member]
Units issued	[4]		45,760,201
Revenues and other						51,664
WES Operating [Member] | Anadarko [Member] | Anadarko Midstream Assets [Member]
Cash payment for acquisition		$ 1,814,000
Acquisitions		$ 193,900
WES Operating [Member] | Affiliates [Member]
Revenues and other			$ 378,437			285,176	[1]
Cost of product	[3]		56,172			34,819
WES Operating [Member] | Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			326,642			222,038	[1]
WES Operating [Member] | Affiliates [Member] | Product Sales [Member]
Revenues and other			$ 50,443			$ 62,507	[1]
WES Operating [Member] | Common Units [Member]
Conversion of units		105,624,704	14,681,388	[4]
Common units outstanding		152,609,285
WES Operating [Member] | Common Units [Member] | Anadarko Midstream Assets [Member]
Units issued		45,760,201	45,760,201	[4]
WES Operating [Member] | Common Units [Member] | Anadarko [Member] | Anadarko Midstream Assets [Member]
Units issued		45,760,201
WES Operating [Member] | Class C Units [Member]
Units issued			308,723
Class C units, common units issued upon conversion		1
Conversion of units	[4]		(14,681,388)
Common units outstanding		14,681,388
Anadarko [Member] | WES Operating [Member]
Ownership interest			2.00%
Anadarko [Member] | Common Units [Member] | WES Operating [Member]
Common units outstanding			6,375,284
Anadarko [Member] | Common Units [Member] | Anadarko Midstream Assets [Member] | WES Operating [Member]
Common units outstanding		6,375,284
WES [Member] | WES Operating [Member]
Ownership interest			98.00%
General partner units owned		2,583,068
WES [Member] | Common Units [Member]
Conversion of units	[6]	178,692,081
Common units outstanding		218,937,797	452,990,862
WES [Member] | Common Units [Member] | WES Operating [Member]
Common units outstanding		50,132,046
WES [Member] | Common Units [Member] | Anadarko Midstream Assets [Member]
Conversion of units		55,360,984

[1] Financial information has been recast to include the financial position and results attributable to AMA. See Note 1 and Note 3.

[2] Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.9 million and $12.7 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.

[3] Represents amounts earned or incurred on and subsequent to the date of the acquisition of Partnership assets, as well as amounts earned or incurred by Anadarko on a historical basis related to the Partnership assets prior to the acquisition of such assets.

[4] See Note 1 for further details on the units issued and converted in connection with the closing of the Merger.

[5] Cost of product includes product purchases from affiliates (as defined in Note 1) of $56.2 million and $34.8 million for the three months ended March 31, 2019 and 2018, respectively. Operation and maintenance includes charges from affiliates of $39.1 million and $23.0 million for the three months ended March 31, 2019 and 2018, respectively. General and administrative includes charges from affiliates of $18.5 million and $12.5 million for the three months ended March 31, 2019 and 2018, respectively. See Note 6.

[6] Total Partnership units issued upon consummation of the Merger exceeds the calculation of such units using the exchange ratio due to the rounding convention reflected in the Merger Agreement.