Acquisitions - Acquisitions Table (details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended						1 Months Ended			1 Months Ended				9 Months Ended	1 Months Ended							1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012		Sep. 30, 2013 Western Gas Partners [Member]	Sep. 30, 2012 Western Gas Partners [Member]		Jan. 31, 2012 Mountain Gas Resources [Member] Western Gas Partners [Member]		Jan. 31, 2012 Mountain Gas Resources [Member] Rendezvous [Member] Western Gas Partners [Member]	Aug. 31, 2012 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]		Jan. 31, 2012 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]		Sep. 30, 2013 Chipeta Processing Limited Liability Company [Member] 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 JV [Member] Western Gas Partners [Member]		Jun. 30, 2013 Mont Belvieu JV [Member] Western Gas Partners [Member] Fractionator [Member]	Sep. 30, 2013 Overland Trail Transmission Limited Liability Company [Member] Western Gas Partners [Member]		Jan. 31, 2012 Common Units [Member] Mountain Gas Resources [Member] Western Gas Partners [Member]		Aug. 31, 2012 Common Units [Member] Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]		Mar. 31, 2013 Common Units [Member] Non-Operated Marcellus Interest [Member] Western Gas Partners [Member]		Jan. 31, 2012 General Partner [Member] Mountain Gas Resources [Member] Western Gas Partners [Member]		Aug. 31, 2012 General Partner [Member] Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]
Business Acquisition [Line Items]
Percentage acquired				100.00%			100.00%	[1]		24.00%	[2]			75.00%	33.75%	[3]	33.75%	[4]				100.00%	[5]
Equity method investment ownership									22.00%										25.00%	[6]
Borrowings	$ 842,566	$ 885,291	[7]				$ 299,000	[1]							$ 250,000	[3]	$ 133,500	[4]				$ 27,500	[5]
Cash on hand							159,587	[1]				128,250	[2]		215,500	[3]			78,129	[6]
Units issued																								632,783	[1]	151,235	[2]	449,129	[3]	12,914	[1]	3,000	[2]
Table Text Block Supplement [Abstract]
Ownership interest by noncontrolling owners														25.00%
GP units issued															9,166
Proceeds from issuance of common and general partner units, net of offering expenses				$ 418,570	$ 211,965	[7]									$ 500
General partner's interest															2.00%
Assets, number of units																					2

[1] The assets acquired from Anadarko consist 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 then remaining 24% membership interest in Chipeta (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) 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” and the acquisition as the “Non-Operated Marcellus Interest acquisition.” In connection with the issuance of WES common units, WES GP purchased 9,166 general partner units for consideration of $0.5 million in order to maintain its 2.0% general partner interest in WES. See Non-Operated Marcellus Interest acquisition below for further information.

[4] The interest acquired from a third party consisted of 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. The interest acquired is referred to as the “Anadarko-Operated Marcellus Interest” and the acquisition as the “Anadarko-Operated Marcellus Interest acquisition.” See Anadarko-Operated Marcellus Interest acquisition below for further information, including the final allocation of the purchase price as of September 30, 2013.

[5] WES acquired Overland Trail Transmission, LLC (“OTTCO”), a Delaware limited liability company, from a third party. OTTCO owns and operates an intrastate pipeline which connects WES’s Red Desert and Granger complexes in southwestern Wyoming. The assets acquired are referred to as the “OTTCO pipeline” and the acquisition as the “OTTCO acquisition.”

[6] The acquisition from a third party consisted of a 25% interest in Enterprise EF78 LLC, an entity formed to design, construct, and own two fractionators located in Mont Belvieu, Texas. The interest acquired is accounted for under the equity method of accounting and is referred to as the “Mont Belvieu JV” and the acquisition as the “Mont Belvieu JV acquisition.” See Mont Belvieu JV acquisition below for further information.

[7] Financial information has been recast to include the financial position and results attributable to the Non-Operated Marcellus Interest. See Note 2.