Acquisitions - Additional Information (details) (USD $)	3 Months Ended
	Mar. 31, 2015		Dec. 31, 2014		Mar. 02, 2015
Business Acquisition [Line Items]
Deferred purchase price obligation - Anadarko	$ 175,696,000	[1]	$ 0	[1],[2]
Western Gas Partners [Member] | Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Post-closing purchase price adjustments	3,500,000
Deferred Purchase Price Obligation - Anadarko [Member] | Western Gas Partners [Member] | Delaware Basin JV Gathering LLC [Member]
Business Acquisition [Line Items]
Future value of deferred purchase price obligation to Anadarko					282,800,000
Deferred purchase price obligation to Anadarko present value					174,276,000	[3]
Discount rate percentage	10.00%
Deferred purchase price obligation - Anadarko	175,700,000
Interest expense, related party	$ 1,400,000

[1] See Note 2.

[2] Financial information has been recast to include the financial position and results attributable to the DBJV system. See Note 1 and Note 2.

[3] WES acquired Anadarko’s interest in Delaware Basin JV Gathering LLC (“DBJV”), which owns a 50% interest in a gathering system and related facilities (the “DBJV system”). The DBJV system is located in the Delaware Basin in Loving, Ward, Winkler and Reeves Counties, Texas. WES will make a cash payment on March 31, 2020, to Anadarko as consideration for the acquisition of DBJV. WES currently estimates the future payment will be $282.8 million, the net present value of which was $174.3 million as of the acquisition date. See Deferred purchase price obligation - Anadarko below.