Acquisitions - Acquisitions Table (details) (USD $)	3 Months Ended			0 Months Ended						1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014		Mar. 03, 2014		Nov. 25, 2014		Mar. 02, 2015		Nov. 30, 2014
Business Acquisition [Line Items]
Borrowings	$ 140,000,000	$ 917,742,000	[1]
Western Gas Partners [Member]
Business Acquisition [Line Items]
Units issued	45,711
Western Gas Partners [Member] | Texas Express And Front Range [Member]
Business Acquisition [Line Items]
Borrowings				350,000,000	[2]
Cash on hand				6,250,000	[2]
Table Text Block Supplement [Abstract]
General partner units issued				6,296
Western Gas Partners [Member] | Texas Express Gathering Limited Liability Company [Member]
Table Text Block Supplement [Abstract]
Equity investment ownership				20.00%
Western Gas Partners [Member] | Texas Express Pipeline Limited Liability Company [Member]
Table Text Block Supplement [Abstract]
Equity investment ownership				20.00%
Western Gas Partners [Member] | Front Range Pipeline Limited Liability Company [Member]
Table Text Block Supplement [Abstract]
Equity investment ownership				33.33%
Western Gas Partners [Member] | Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired						100.00%	[3]
Borrowings						475,000,000	[3]
Cash on hand						298,327,000	[3]
Western Gas Partners [Member] | Delaware Basin JV Gathering LLC [Member]
Business Acquisition [Line Items]
Percentage acquired	50.00%							50.00%	[4]
Western Gas Partners [Member] | Common Units [Member] | Texas Express And Front Range [Member]
Business Acquisition [Line Items]
Units issued				308,490	[2]
Western Gas Partners [Member] | Class C Units [Member]
Business Acquisition [Line Items]
Units issued	45,711
Table Text Block Supplement [Abstract]
Proceeds from the issuance of units										750,000,000
Western Gas Partners [Member] | Class C Units [Member] | Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Units issued						10,913,853	[3]
Western Gas Partners [Member] | General Partner [Member]
Business Acquisition [Line Items]
Percentage acquired	100.00%
Units issued										153,061	[5],[6]
Western Gas Partners [Member] | General Partner [Member] | Texas Express And Front Range [Member]
Table Text Block Supplement [Abstract]
Proceeds from the issuance of units				400,000
Deferred Purchase Price Obligation - Anadarko [Member] | Western Gas Partners [Member] | Delaware Basin JV Gathering LLC [Member]
Business Acquisition [Line Items]
Deferred purchase price obligation to Anadarko present value								174,276,000	[4]
Table Text Block Supplement [Abstract]
Future value of deferred purchase price obligation to Anadarko								282,800,000

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

[2] WES acquired a 20% interest in each of TEG and TEP and a 33.33% interest in FRP from Anadarko. These assets gather and transport NGLs primarily from the Anadarko and Denver-Julesburg (“DJ”) Basins. The interests in these entities are accounted for under the equity method of accounting. In connection with the issuance of WES common units, WES GP purchased 6,296 general partner units in exchange for WES GP’s proportionate capital contribution of $0.4 million.

[3] WES acquired Nuevo Midstream, LLC (“Nuevo”) from a third party. Following the acquisition, WES changed the name of Nuevo to Delaware Basin Midstream, LLC (“DBM”). The assets acquired include cryogenic processing plants, a gas gathering system, and related facilities and equipment, which are collectively referred to as the “DBM complex” and serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico.

[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 Deferred purchase price obligation - Anadarko below.

[5] Represents general partner units of WES issued to WES GP in exchange for WES GP’s proportionate capital contribution.

[6] Includes the issuance of 1,120,153 WES common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, WES GP elected not to make a corresponding capital contribution to maintain its 2.0% interest in WES.