Acquisitions - Additional Information (details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			1 Months Ended		12 Months Ended		1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Anadarko-Operated Marcellus Interest [Member] Western Gas Partners [Member]		Dec. 31, 2013 Anadarko-Operated Marcellus Interest [Member] Western Gas Partners [Member]	Dec. 31, 2013 Anadarko-Operated Marcellus Interest [Member] Purchase Price Allocation Adjustments [Member] Western Gas Partners [Member]	Dec. 31, 2008 Newcastle [Member] Western Gas Partners [Member]	Dec. 31, 2013 Newcastle [Member] Western Gas Partners [Member]	Dec. 31, 2013 Fort Union [Member] Western Gas Partners [Member]	Dec. 31, 2008 Fort Union [Member] Western Gas Partners [Member]	Aug. 31, 2012 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]	Jul. 31, 2009 Chipeta Processing Limited Liability Company [Member] Western Gas Partners [Member]	Sep. 30, 2010 White Cliffs [Member] Western Gas Partners [Member]
Business Acquisition [Line Items]
Equity method investment ownership										14.81%	14.81%			10.00%
Percentage acquired				33.75%	[1]			50.00%	50.00%			24.00%	51.00%
Revenues	$ 1,053,495	$ 910,587	$ 869,405			$ 14,100
Operating expenses	735,566	716,209	624,111			700
Purchase price adjustment						$ 134,645	$ 1,100

[1] 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” 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.