Acquisitions - Acquisitions Table (details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended						1 Months Ended							1 Months Ended							1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013		Mar. 31, 2014 Western Gas Partners [Member]	Mar. 31, 2013 Western Gas Partners [Member]		Mar. 31, 2013 Non-Operated Marcellus Interest [Member] Western Gas Partners [Member]		Mar. 31, 2013 Anadarko-Operated Marcellus Interest [Member] Western Gas Partners [Member]		Jun. 30, 2013 Mont Belvieu Joint Venture [Member] Western Gas Partners [Member]		Jun. 30, 2013 Mont Belvieu Joint Venture [Member] Western Gas Partners [Member] Fractionator [Member]	Sep. 30, 2013 Overland Trail Transmission Limited Liability Company [Member] Western Gas Partners [Member]		Mar. 31, 2014 Texas Express And Front Range [Member] Western Gas Partners [Member]		Mar. 31, 2014 Texas Express Gathering Limited Liability Company [Member] Western Gas Partners [Member]	Mar. 31, 2014 Texas Express Pipeline Limited Liability Company [Member] Western Gas Partners [Member]	Mar. 31, 2014 Front Range Pipeline Limited Liability Company [Member] Western Gas Partners [Member]	Mar. 31, 2013 Common Units [Member] Non-Operated Marcellus Interest [Member] Western Gas Partners [Member]		Mar. 31, 2014 Common Units [Member] Texas Express And Front Range [Member] Western Gas Partners [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	$ 917,742	$ 384,946	[5]				$ 250,000	[1]	$ 133,500	[2]				$ 27,500	[3]	$ 350,000	[6]
Cash on hand							215,500	[1]	1,145	[2]	78,129	[4]				6,250	[6]
Units issued																					449,129	[1]	308,490	[6]
Table Text Block Supplement [Abstract]
GP units issued							9,166									6,296
Proceeds from issuance of common and general partner units, net of offering expenses				$ 17,530	$ 0	[5]	$ 500									$ 400
General partner's interest							2.00%
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.”

[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 DJ Basin. 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.