Transactions with Affiliates - Summary of Affiliate Transactions Table (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017		Jun. 30, 2016
Related Party Transaction [Line Items]
Revenues and other		$ 525,450	$ 428,664	$ 1,041,643		$ 811,805
Equity income, net – affiliates	[1]	21,728	19,693	41,189		36,507
Cost of product	[2]	203,277	104,849	392,636		181,316
Operation and maintenance	[2]	76,148	75,173	149,908		151,386
General and administrative	[2]	11,197	11,887	24,673		24,402
Operating expenses		379,755	273,710	903,088		520,868
Interest income	[3]	4,225	4,225	8,450		8,450
Interest expense	[4]	36,297	13,429	72,330		45,568
Distributions to unitholders	[5]			208,803		181,156
Above-market component of swap agreements with Anadarko		16,373	9,552	28,670	[5]	16,365	[5]
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[1]	316,313	302,405	631,468		574,989
Cost of product	[1]	21,607	22,145	37,595		46,725
Operation and maintenance	[6]	18,462	17,661	35,551		35,636
General and administrative	[7]	9,489	9,374	19,223		18,524
Operating expenses		49,558	49,180	92,369		100,885
Interest expense	[8]	0	(15,461)	71		(10,924)
Settlement of the Deferred purchase price obligation - Anadarko	[9]			(37,346)		0
Distributions to unitholders	[10]	87,731	80,973	170,328		158,125
Affiliates [Member] | Western Gas Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[11]	1,760	1,639	3,490		2,245
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	$ (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 $21.6 million and $37.6 million for the three and six months ended June 30, 2017, respectively, and $22.1 million and $46.7 million for the three and six months ended June 30, 2016, respectively. Operation and maintenance includes charges from Anadarko of $18.5 million and $35.6 million for the three and six months ended June 30, 2017, respectively, and $17.7 million and $35.6 million for the three and six months ended June 30, 2016, respectively. General and administrative includes charges from Anadarko of $9.5 million and $19.2 million for the three and six months ended June 30, 2017, respectively, and $9.4 million and $18.5 million for the three and six months ended June 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 six months ended June 30, 2017, respectively, and $15.5 million and $10.9 million for the three and six months ended June 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).