Description of Business and Basis of Presentation - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended	9 Months Ended				12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018		Sep. 30, 2017		Dec. 31, 2017	Jan. 01, 2018	May 31, 2008
Revenues and other		$ 507,762,000	$ 574,695,000		$ 1,432,483,000		$ 1,616,338,000
Cost of product	[1]	105,966,000	239,223,000		303,518,000		631,859,000
Note receivable - Anadarko		260,000,000			260,000,000				$ 260,000,000
Impairments		25,317,000	2,159,000		152,708,000		170,079,000		$ 178,400,000
Loss on divestiture and other, net	[2]	(65,000)	(72,000)		(351,000)	[3]	(135,017,000)	[3]
Proceeds from property insurance claims					0		22,977,000
Cumulative effect of accounting change	[4]	(44,379,000)			(44,379,000)
Accounting Standards Update 2014-09 [Member]
Cumulative effect of accounting change										$ (44,379,000)
Service Revenues - Fee Based [Member]
Revenues and other		409,106,000			1,146,099,000
Product Sales [Member]
Revenues and other		$ 75,150,000			$ 217,738,000
Chipeta [Member]
Ownership interest by noncontrolling interest owner		25.00%			25.00%
Affiliates [Member]
Revenues and other	[5]	$ 274,514,000	351,127,000		$ 766,179,000		982,595,000
Cost of product	[5]	46,971,000	22,902,000		131,428,000		60,497,000
Affiliates [Member] | Service Revenues - Fee Based [Member]
Revenues and other		204,090,000	157,303,000		582,579,000		484,601,000
Affiliates [Member] | Product Sales [Member]
Revenues and other		69,723,000	$ 185,002,000		$ 182,372,000		489,172,000
Prior Period Adjustment [Member]
Cost of product				$ 51,600,000
Prior Period Adjustment [Member] | Service Revenues - Fee Based [Member]
Revenues and other				39,000,000
Prior Period Adjustment [Member] | Product Sales [Member]
Revenues and other				$ 12,600,000
Western Gas Equity Partners, LP [Member] | Western Gas Partners, LP [Member] | General Partner [Member]
Percentage ownership interest					100.00%
Western Gas Partners, LP [Member] | Maximum [Member]
Contract terms					Payment is generally received from the customer in the month following the service or delivery of the product. Contracts with customers generally have initial terms ranging from 5 to 10 years.
Western Gas Partners, LP [Member] | Kitty Draw and Third Creek Gathering Systems [Member]
Impairments		6,800,000			$ 134,000,000
Western Gas Partners, LP [Member] | Delaware Basin Midstream Complex [Member]
Loss on divestiture and other, net							5,700,000
Proceeds from insurance claims, total							52,900,000
Proceeds from business interruption insurance claims							29,882,000
Proceeds from property insurance claims							$ 22,977,000
Western Gas Partners, LP [Member] | Affiliates [Member]
Note receivable - Anadarko		260,000,000			260,000,000						$ 260,000,000
Western Gas Partners, LP [Member] | Affiliates [Member] | Product Sales [Member] | Kitty Draw and Third Creek Gathering Systems [Member]
Revenues and other		$ 0			$ (10,900,000)
Western Gas Partners, LP [Member] | Other Subsidiaries of Anadarko [Member]
WES common units issued					2,011,380

[1] Cost of product includes product purchases from affiliates (as defined in Note 1) of $47.0 million and $131.4 million for the three and nine months ended September 30, 2018, respectively, and $22.9 million and $60.5 million for the three and nine months ended September 30, 2017, respectively. Operation and maintenance includes charges from affiliates of $25.1 million and $68.8 million for the three and nine months ended September 30, 2018, respectively, and $18.1 million and $53.7 million for the three and nine months ended September 30, 2017, respectively. General and administrative includes charges from affiliates of $11.8 million and $35.0 million for the three and nine months ended September 30, 2018, respectively, and $10.4 million and $29.6 million for the three and nine months ended September 30, 2017, respectively. See Note 6.

[2] Includes losses related to an incident at the DBM complex for the nine months ended September 30, 2017. See Note 1.

[3] Includes losses related to an incident at the DBM complex for the nine months ended September 30, 2017. See Note 1.

[4] See Note 1.

[5] Represents amounts earned or incurred on and subsequent to the date of the acquisition of WES assets, as well as amounts earned or incurred by Anadarko on a historical basis related to WES assets prior to the acquisition of such assets by WES, recognized under gathering, treating or processing agreements, and purchase and sale agreements.