Acquisitions and Divestitures - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	[3]	Mar. 02, 2015	Dec. 31, 2014	[2]
Property, Plant and Equipment [Line Items]
Deferred purchase price obligation - Anadarko	[1]	$ 184,196		$ 184,196				$ 0
Gain on divestiture, net		77,244	$ 0	77,244	$ 0
Western Gas Partners, LP [Member] | Dew and Pinnacle Systems [Member]
Property, Plant and Equipment [Line Items]
Proceeds from the sale of assets				146,700
Gain on divestiture, net				77,200
Western Gas Partners, LP [Member] | Delaware Basin Midstream LLC [Member]
Property, Plant and Equipment [Line Items]
Post-closing purchase price adjustments				$ 3,500
Western Gas Partners, LP [Member] | Deferred Purchase Price Obligation - Anadarko [Member] | Delaware Basin JV Gathering LLC [Member]
Property, Plant and Equipment [Line Items]
Discount rate percentage				10.00%
Deferred purchase price obligation - Anadarko		184,200		$ 184,200
Interest expense, related party		$ 4,300		$ 9,900
Level 3 inputs [Member] | Western Gas Partners, LP [Member] | Deferred Purchase Price Obligation - Anadarko [Member] | Delaware Basin JV Gathering LLC [Member]
Property, Plant and Equipment [Line Items]
Deferred purchase price obligation to Anadarko - future value							$ 282,800
Deferred purchase price obligation to Anadarko - acquisition date value	[4]						$ 174,276

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

[4] 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 DBJV acquisition—Deferred purchase price obligation - Anadarko below.