Transactions with Affiliates - Summary of Affiliate Transactions Table (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Revenues and other		$ 2,248,356	$ 1,804,270	$ 1,752,072
Equity income, net – affiliates	[1]	85,194	78,717	71,251
Cost of product	[2]	908,693	494,194	528,369
Operation and maintenance	[2]	315,994	308,010	331,972
General and administrative	[2]	50,668	49,248	44,428
Operating expenses		1,791,421	1,180,081	1,726,165
Interest income	[3]	16,900	16,900	16,900
Interest expense	[4]	144,615	116,628	113,874
Distributions to unitholders	[5]	441,967	374,082	306,477
Above-market component of swap agreements with Anadarko	[5]	58,551	45,820	18,449
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[1]	1,365,318	1,228,232	1,220,639
Cost of product	[1]	86,010	80,455	167,354
Operation and maintenance	[6]	72,489	72,330	77,061
General and administrative	[7]	39,940	38,873	34,703
Operating expenses		198,439	191,658	279,118
Interest expense	[8]	71	(7,747)	14,400
Settlement of the Deferred purchase price obligation - Anadarko	[9]	(37,346)	0	0
Distributions to unitholders	[10]	360,523	315,505	269,029
Affiliates [Member] | Western Gas Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[11]	7,100	5,614	2,235
Affiliates [Member] | Deferred Purchase Price Obligation - Anadarko [Member]
Related Party Transaction [Line Items]
Settlement of the Deferred purchase price obligation - Anadarko	[12]	$ (37,346)	$ 0	$ 0

[1] 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.

[2] Cost of product includes product purchases from Anadarko (as defined in Note 1) of $86.0 million, $80.5 million and $167.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. Operation and maintenance includes charges from Anadarko of $72.5 million, $72.3 million and $77.1 million for the years ended December 31, 2017, 2016 and 2015, respectively. General and administrative includes charges from Anadarko of $39.9 million, $38.9 million and $34.7 million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 5.

[3] Represents interest income recognized on the note receivable from Anadarko.

[4] Includes affiliate (as defined in Note 1) amounts of $(0.1) million, $7.7 million and $(14.4) million for the years ended December 31, 2017, 2016 and 2015, respectively. See Note 2 and Note 12.

[5] See Note 5.

[6] Represents expenses incurred on and subsequent to the date of the acquisition of WES assets, as well as expenses incurred by Anadarko on a historical basis related to WES assets prior to the acquisition of such assets by WES.

[7] Represents general and administrative expense incurred on and subsequent to the date of the acquisition of WES assets, as well as a management services fee for reimbursement of expenses incurred by Anadarko for periods prior to the acquisition of WES assets by WES. These amounts include equity-based compensation expense allocated to WES and WGP by Anadarko (see WES LTIP and WGP LTIP and Anadarko Incentive Plans within this Note 5) and amounts charged by Anadarko under the WGP and WES omnibus agreements.

[8] Includes amounts related to the Deferred purchase price obligation - Anadarko (see Note 2 and Note 12) and for the year ended December 31, 2015, includes interest expense recognized on the WGP WCF (see Note 12).

[9] See Note 2.

[10] Represents distributions paid under WGP’s partnership agreement (see Note 3 and Note 4).

[11] Represents distributions paid to other subsidiaries of Anadarko under WES’s partnership agreement (see Note 3 and Note 4).

[12] Represents the cash payment to Anadarko for the settlement of the Deferred purchase price obligation - Anadarko (see Note 2).