Transactions with Affiliates - Summary of Affiliate Transactions Table (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Revenues and other		$ 437,168	$ 516,193
Equity income, net – affiliates	[1]	20,424	19,461
Cost of product	[2]	77,799	189,359
Operation and maintenance	[2]	88,279	73,760
General and administrative	[2]	14,964	13,476
Operating expenses		270,414	523,333
Interest income	[3]	4,225	4,225
Interest expense	[4]	40,346	36,033
Distributions to unitholders	[5]	120,140	101,254
Above-market component of swap agreements with Anadarko	[5]	14,282	12,297
Affiliates [Member]
Related Party Transaction [Line Items]
Revenues and other	[1]	241,062	315,155
Cost of product	[1]	20,244	15,988
Operation and maintenance	[6]	20,248	17,089
General and administrative	[7]	11,823	9,734
Operating expenses		52,315	42,811
Interest expense	[8]	0	71
Distributions to unitholders	[9]	98,000	82,597
Affiliates [Member] | Western Gas Partners, LP [Member]
Related Party Transaction [Line Items]
Distributions to unitholders	[10]	$ 1,850	$ 1,730

[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 $20.2 million and $16.0 million for the three months ended March 31, 2018 and 2017, respectively. Operation and maintenance includes charges from Anadarko of $20.2 million and $17.1 million for the three months ended March 31, 2018 and 2017, respectively. General and administrative includes charges from Anadarko of $11.8 million and $9.7 million for the three months ended March 31, 2018 and 2017, respectively. See Note 6.

[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 months ended March 31, 2018 and 2017, respectively. See Note 10.

[5] See Note 6.

[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 Anadarko Incentive Plan within this Note 6) 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 3 and Note 10).

[9] Represents distributions paid under WGP’s partnership agreement (see Note 4 and Note 5).

[10] Represents distributions paid to other subsidiaries of Anadarko under WES’s partnership agreement (see Note 4 and Note 5).