Acquisitions - Acquisitions Table (details) (USD $)	9 Months Ended						0 Months Ended			0 Months Ended			0 Months Ended					0 Months Ended								0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013		Sep. 30, 2014 Western Gas Partners [Member]	Sep. 30, 2013 Western Gas Partners [Member]		Mar. 01, 2013 Western Gas Partners [Member] Non-Operated Marcellus Interest [Member]		Mar. 01, 2013 Western Gas Partners [Member] Non-Operated Marcellus Interest [Member]	Mar. 08, 2013 Western Gas Partners [Member] Anadarko-Operated Marcellus Interest [Member]		Mar. 08, 2013 Western Gas Partners [Member] Anadarko-Operated Marcellus Interest [Member]	Jun. 05, 2013 Western Gas Partners [Member] Mont Belvieu Joint Venture [Member]		Jun. 05, 2013 Western Gas Partners [Member] Mont Belvieu Joint Venture [Member]		Jun. 05, 2013 Western Gas Partners [Member] Mont Belvieu Joint Venture [Member] Fractionator [Member] unit	Sep. 03, 2013 Western Gas Partners [Member] Overland Trail Transmission Limited Liability Company [Member]		Mar. 03, 2014 Western Gas Partners [Member] Texas Express And Front Range [Member]		Mar. 03, 2014 Western Gas Partners [Member] Texas Express And Front Range [Member]	Mar. 03, 2014 Western Gas Partners [Member] Texas Express Gathering Limited Liability Company [Member]	Mar. 03, 2014 Western Gas Partners [Member] Texas Express Pipeline Limited Liability Company [Member]	Mar. 03, 2014 Western Gas Partners [Member] Front Range Pipeline Limited Liability Company [Member]	Mar. 01, 2013 Western Gas Partners [Member] Common Units [Member] Non-Operated Marcellus Interest [Member]		Mar. 03, 2014 Western Gas Partners [Member] Common Units [Member] Texas Express And Front Range [Member]
Business Acquisition [Line Items]
Percentage acquired				100.00%			33.75%	[1]		33.75%	[2]							100.00%	[3]
Equity investment ownership															25.00%	[4]							20.00%	20.00%	33.33%
Borrowings	$ 1,136,878,000	$ 842,566,000	[5]				$ 250,000,000	[1]		$ 133,500,000	[2]							$ 27,500,000	[3]	$ 350,000,000	[6]
Cash on hand							215,500,000	[1]					78,129,000	[4]						6,250,000	[6]
Units issued																										449,129	[1]	308,490	[6]
Table Text Block Supplement [Abstract]
WES general partner units issued									9,166													6,296
Proceeds from issuance of common and general partner units, net of offering expenses				99,035,000	418,570,000	[5]	500,000													400,000
General partner's interest				2.00%			2.00%
Purchase price adjustment												$ 1,100,000
Assets, number of units																	2

[1] WES acquired Anadarko’s 33.75% interest (non-operated) in the Liberty and Rome gas gathering systems, serving production from the Marcellus shale in north-central Pennsylvania. The interest acquired is referred to as the “Non-Operated Marcellus Interest.” In connection with the issuance of WES common units, WES GP purchased 9,166 general partner units for consideration of $0.5 million to maintain its 2.0% general partner interest in WES.

[2] WES acquired a 33.75% interest in each of the Larry’s Creek, Seely and Warrensville gas gathering systems, which are operated by Anadarko and serve production from the Marcellus shale in north-central Pennsylvania, from a third party. The interest acquired is referred to as the “Anadarko-Operated Marcellus Interest.” 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.

[3] 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.

[4] 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.

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

[6] 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 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 for consideration of $0.4 million to maintain its 2.0% general partner interest in WES.