Acquisitions - Acquisitions Table (details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			0 Months Ended				1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 13, 2012		Aug. 01, 2012		Jul. 31, 2009	Mar. 01, 2013		Mar. 08, 2013		Jun. 05, 2013		Sep. 03, 2013		Mar. 03, 2014		Nov. 25, 2014
Business Acquisition [Line Items]
Borrowings	$ 1,648,028	$ 957,503	$ 1,041,648
Cash on hand		78,129
Western Gas Partners [Member]
Business Acquisition [Line Items]
Percentage acquired	100.00%
Western Gas Partners [Member] | Mountain Gas Resources [Member]
Business Acquisition [Line Items]
Percentage acquired				100.00%	[1]
Borrowings				299,000	[1]
Cash on hand				159,587	[1]
Western Gas Partners [Member] | Mountain Gas Resources [Member] | Rendezvous [Member]
Business Acquisition [Line Items]
Equity investment ownership				22.00%
Western Gas Partners [Member] | Chipeta Processing Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired	75.00%					24.00%	[2]	51.00%
Cash on hand						128,250	[2]
Table Text Block Supplement [Abstract]
Ownership interest by noncontrolling owner	25.00%
Western Gas Partners [Member] | Non-Operated Marcellus Interest [Member]
Business Acquisition [Line Items]
Percentage acquired	33.75%								33.75%	[3]
Borrowings									250,000	[3]
Cash on hand									215,500	[3]
Table Text Block Supplement [Abstract]
General partner units issued									9,166
Western Gas Partners [Member] | Anadarko-Operated Marcellus Interest [Member]
Business Acquisition [Line Items]
Percentage acquired	33.75%										33.75%	[4]
Borrowings											133,500	[4]
Table Text Block Supplement [Abstract]
Purchase price adjustment											1,100
Western Gas Partners [Member] | Mont Belvieu Joint Venture [Member]
Business Acquisition [Line Items]
Equity investment ownership													25.00%	[5]
Cash on hand													78,129	[5]
Western Gas Partners [Member] | Mont Belvieu Joint Venture [Member] | Fractionation Train [Member]
Table Text Block Supplement [Abstract]
Assets, number of units													2
Western Gas Partners [Member] | Overland Trail Transmission Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired															100.00%	[6]
Borrowings															27,500	[6]
Western Gas Partners [Member] | Texas Express And Front Range [Member]
Business Acquisition [Line Items]
Borrowings																	350,000	[7]
Cash on hand																	6,250	[7]
Table Text Block Supplement [Abstract]
General partner units issued																	6,296
Western Gas Partners [Member] | Texas Express Gathering Limited Liability Company [Member]
Business Acquisition [Line Items]
Equity investment ownership																	20.00%
Western Gas Partners [Member] | Texas Express Pipeline Limited Liability Company [Member]
Business Acquisition [Line Items]
Equity investment ownership																	20.00%
Western Gas Partners [Member] | Front Range Pipeline Limited Liability Company [Member]
Business Acquisition [Line Items]
Equity investment ownership																	33.33%
Western Gas Partners [Member] | Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Percentage acquired																			100.00%	[8]
Borrowings																			475,000	[8]
Cash on hand																			298,327	[8]
Table Text Block Supplement [Abstract]
Purchase price adjustment	1,553,959
Western Gas Partners [Member] | Common Units [Member] | Mountain Gas Resources [Member]
Business Acquisition [Line Items]
Units issued				632,783	[1]
Western Gas Partners [Member] | Common Units [Member] | Chipeta Processing Limited Liability Company [Member]
Business Acquisition [Line Items]
Units issued						151,235	[2]
Western Gas Partners [Member] | Common Units [Member] | Non-Operated Marcellus Interest [Member]
Business Acquisition [Line Items]
Units issued									449,129	[3]
Western Gas Partners [Member] | Common Units [Member] | Texas Express And Front Range [Member]
Business Acquisition [Line Items]
Units issued																	308,490	[7]
Western Gas Partners [Member] | Class C Units [Member]
Business Acquisition [Line Items]
Class C units issued	10,913,853
Table Text Block Supplement [Abstract]
Proceeds from the issuance of units	750,000	0	0																750,000
Western Gas Partners [Member] | Class C Units [Member] | Delaware Basin Midstream Limited Liability Company [Member]
Business Acquisition [Line Items]
Class C units issued																			10,913,853	[8]
Western Gas Partners [Member] | General Partner [Member] | Mountain Gas Resources [Member]
Business Acquisition [Line Items]
Units issued				12,914	[1]
Western Gas Partners [Member] | General Partner [Member] | Chipeta Processing Limited Liability Company [Member]
Business Acquisition [Line Items]
Units issued						3,086	[2]
Western Gas Partners [Member] | General Partner [Member] | Non-Operated Marcellus Interest [Member]
Table Text Block Supplement [Abstract]
Proceeds from the issuance of units									500
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

[1] The assets acquired from Anadarko consisted of (i) the “Red Desert complex,” which is located in the greater Green River Basin in southwestern Wyoming, and includes the Patrick Draw processing plant, the Red Desert processing plant, gathering lines, and related facilities, (ii) a 22% interest in Rendezvous, which owns a gathering system serving the Jonah and Pinedale Anticline fields in southwestern Wyoming, and (iii) certain additional midstream assets and equipment. These assets are collectively referred to as the “MGR assets” and the acquisition as the “MGR acquisition.”

[2] WES acquired Anadarko’s additional Chipeta interest (as described in Note 1). WES received distributions related to the additional interest beginning July 1, 2012. This transaction brought WES’s total membership interest in Chipeta to 75%. The remaining 25% membership interest in Chipeta held by a third-party member is reflected as noncontrolling interests in the consolidated financial statements for all periods presented.

[3] WES acquired Anadarko’s 33.75% interest (non-operated) (the “Non-Operated Marcellus Interest”) in the Liberty and Rome gas gathering systems (the “Non-Operated Marcellus Interest systems”), serving production from the Marcellus shale in North-central Pennsylvania. In connection with the issuance of WES common units, WES GP purchased 9,166 general partner units for consideration of $0.5 million.

[4] WES acquired a 33.75% interest (the “Anadarko-Operated Marcellus Interest”) in each of the Larry’s Creek, Seely and Warrensville gas gathering systems (the “Anadarko-Operated Marcellus Interest systems”), which are operated by Anadarko and serve production from the Marcellus shale in North-central Pennsylvania, from a third party. During the third quarter of 2013, WES recorded a $1.1 million decrease in the assets acquired and liabilities assumed in the acquisition, representing the final purchase price allocation.

[5] WES acquired a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas, from a third party. The interest acquired is accounted for under the equity method of accounting.

[6] WES acquired Overland Trail Transmission, LLC (“OTTCO”), a Delaware limited liability company, from a third party. OTTCO owns and operates an intrastate pipeline that connects WES’s Red Desert and Granger complexes in southwestern Wyoming.

[7] 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.

[8] 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 serve production from Reeves, Loving and Culberson Counties, Texas and Eddy and Lea Counties, New Mexico. These assets are referred to collectively as the “DBM complex.” See Note 4 for a discussion of the WES Class C units.