Transactions with Affiliates - Summary of Affiliate Transactions Table (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Related Party Transaction [Line Items]
Revenues and other		$ 574,695	$ 481,645	$ 1,616,338		$ 1,293,450
Equity income, net – affiliates	[1]	21,519	20,294	62,708		56,801
Cost of product	[2]	239,223	145,643	631,859		326,959
Operation and maintenance	[2]	79,536	74,755	229,444		226,141
General and administrative	[2]	12,922	12,112	37,595		36,514
Operating expenses		417,594	312,818	1,320,682		833,686
Interest income	[3]	4,225	4,225	12,675		12,675
Interest expense	[4]	36,117	31,301	108,447		76,869
Distributions to unitholders	[5]			324,290		276,114
Above-market component of swap agreements with Anadarko		18,049	18,417	46,719	[5]	34,782	[5]
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[1]	351,127	325,312	982,595		900,301
Cost of product	[1]	22,902	21,254	60,497		67,979
Operation and maintenance	[6]	18,110	15,052	53,661		50,688
General and administrative	[7]	10,414	9,655	29,637		28,179
Operating expenses		51,426	45,961	143,795		146,846
Interest expense	[8]	0	(1,173)	71		(12,097)
Settlement of the Deferred purchase price obligation - Anadarko	[9]			(37,346)		0
Distributions to unitholders	[10]	94,205	77,462	264,533		235,587
Affiliates [Member] | Western Gas Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[11]	1,790	1,670	5,280		3,915
Affiliates [Member] | Deferred Purchase Price Obligation - Anadarko [Member]
Related Party Transaction [Line Items]
Settlement of the Deferred purchase price obligation - Anadarko	[12]	$ 0	$ 0	$ (37,346)		$ 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 $22.9 million and $60.5 million for the three and nine months ended September 30, 2017, respectively, and $21.3 million and $68.0 million for the three and nine months ended September 30, 2016, respectively. Operation and maintenance includes charges from Anadarko of $18.1 million and $53.7 million for the three and nine months ended September 30, 2017, respectively, and $15.1 million and $50.7 million for the three and nine months ended September 30, 2016, respectively. General and administrative includes charges from Anadarko of $10.4 million and $29.6 million for the three and nine months ended September 30, 2017, respectively, and $9.7 million and $28.2 million for the three and nine months ended September 30, 2016, 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 zero and $(0.1) million for the three and nine months ended September 30, 2017, respectively, and $1.2 million and $12.1 million for the three and nine months ended September 30, 2016, respectively. See Note 2 and Note 9.

[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 WES’s 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 Plan within this Note 5) and amounts charged by Anadarko under the WGP and WES omnibus agreements.

[8] Includes amounts related to WES’s Deferred purchase price obligation - Anadarko (see Note 2 and Note 9).

[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).