Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended				6 Months Ended			12 Months Ended
		Feb. 28, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Jun. 30, 2019	Jun. 30, 2018		Dec. 31, 2018
Acquisitions							$ 92,546
Common units outstanding			453,008,854				453,008,854			218,937,797
Conversion ratio per unit		1.525
Revenues and other			$ 685,054		$ 518,078	[1]	$ 1,356,937	$ 1,019,132	[1]
Cost of product	[2]		122,877		95,656	[1]	236,940	189,974	[1]
Impairments			$ 797		127,184	[1]	$ 1,187	127,384	[1]	$ 230,600
Kitty Draw and Third Creek Gathering Systems [Member]
Impairments								127,200
Prior Period Adjustment [Member]
Cost of product					32,000			51,600
Prior Period Adjustment [Member] | Service Revenues - Fee Based [Member]
Revenues and other					24,700			39,000
Prior Period Adjustment [Member] | Product Sales [Member]
Revenues and other					7,300			12,600
Chipeta [Member]
Ownership interest by noncontrolling interest owner			25.00%				25.00%
WES Operating [Member]
Ownership interest by noncontrolling interest owner			2.00%				2.00%
Anadarko Midstream Assets [Member]
Conversion ratio per unit		1.4056
Revenues and other					58,686			110,350
Affiliates [Member]
Revenues and other			$ 385,184		289,544	[1]	$ 763,621	574,720	[1]
Cost of product			68,225		38,001		124,397	72,820
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			343,484		234,512	[1]	670,126	456,550	[1]
Affiliates [Member] | Product Sales [Member]
Revenues and other			$ 41,066		54,494	[1]	$ 91,509	117,001	[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				0			2,583,068
Conversion of units							0
Revenues and other			$ 685,054		518,078	[1]	$ 1,356,937	1,019,132	[1]
Cost of product	[3]		122,877		95,656	[1]	236,940	189,974	[1]
Impairments			797		127,184	[1]	$ 1,187	127,384	[1]
WES Operating [Member] | Anadarko Midstream Assets [Member]
Units issued							45,760,201
Revenues and other					58,686			110,350
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			385,184		289,544	[1]	$ 763,621	574,720	[1]
Cost of product			68,200		38,000		124,400	72,800
WES Operating [Member] | Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other			343,484		234,512	[1]	670,126	456,550	[1]
WES Operating [Member] | Affiliates [Member] | Product Sales [Member]
Revenues and other			$ 41,066		$ 54,494	[1]	$ 91,509	$ 117,001	[1]
WES Operating [Member] | Common Units [Member]
Conversion of units		105,624,704					14,681,388
Common units outstanding		152,609,285
WES Operating [Member] | Common Units [Member] | Anadarko Midstream Assets [Member]
Units issued		45,760,201					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							(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			6,400,000				6,400,000
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		178,692,081
Common units outstanding		452,990,862								218,937,797
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 $68.2 million and $124.4 million for the three and six months ended June 30, 2019, respectively, and $38.0 million and $72.8 million for the three and six months ended June 30, 2018, respectively. Operation and maintenance includes charges from affiliates of $32.3 million and $71.5 million for the three and six months ended June 30, 2019, respectively, and $26.8 million and $49.8 million for the three and six months ended June 30, 2018, respectively. General and administrative includes charges from affiliates of $26.9 million and $45.8 million for the three and six months ended June 30, 2019, respectively, and $12.3 million and $25.0 million for the three and six months ended June 30, 2018, respectively. See Note 6.

[3] Cost of product includes product purchases from affiliates (as defined in Note 1) of $68.2 million and $124.4 million for the three and six months ended June 30, 2019, respectively, and $38.0 million and $72.8 million for the three and six months ended June 30, 2018, respectively. Operation and maintenance includes charges from affiliates of $32.3 million and $71.5 million for the three and six months ended June 30, 2019, respectively, and $26.8 million and $49.8 million for the three and six months ended June 30, 2018, respectively. General and administrative includes charges from affiliates of $26.4 million and $44.9 million for the three and six months ended June 30, 2019, respectively, and $12.0 million and $24.5 million for the three and six months ended June 30, 2018, respectively. See Note 6.