Summary of Significant Accounting Policies - Equity Method Investment Table (details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Balance	$ 243,619		$ 106,130
Contributions	51,974		862		93
Balance	106,130
Fort Union [Member] | Western Gas Partners [Member]
Schedule of Equity Method Investments [Line Items]
Balance	25,172	[1]	23,453	[1]
Initial investment		[1]
Investment earnings, net of amortization	6,273	[1]	6,383	[1]
Contributions	16	[1]		[1]
Distributions	(4,570)	[1]	(5,198)	[1]
Distributions in excess of cumulative earnings		[1]
Balance	23,453	[1]	22,268	[1]
Table Text Block Supplement [Abstract]
Approval Percentage	65.00%
White Cliffs [Member] | Western Gas Partners [Member]
Schedule of Equity Method Investments [Line Items]
Balance	35,039	[2]	17,567	[2]
Initial investment		[2]
Investment earnings, net of amortization	9,681	[2]	7,871	[2]
Contributions	19,087	[2]	862	[2]
Distributions	(9,266)	[2]	(8,876)	[2]
Distributions in excess of cumulative earnings	(2,030)	[2]
Balance	17,567	[2]	17,710	[2]
Table Text Block Supplement [Abstract]
Approval Percentage	75.00%
Rendezvous [Member] | Western Gas Partners [Member]
Schedule of Equity Method Investments [Line Items]
Balance	60,928	[3]	65,110	[3]
Initial investment		[3]
Investment earnings, net of amortization	2,088	[3]	1,857	[3]
Contributions		[3]		[3]
Distributions	(4,029)	[3]	(6,586)	[3]
Distributions in excess of cumulative earnings	(2,241)	[3]
Balance	65,110	[3]	69,839	[3]
Table Text Block Supplement [Abstract]
Approval Percentage	100.00%
Mont Belvieu Joint Venture [Member] | Western Gas Partners [Member]
Schedule of Equity Method Investments [Line Items]
Balance	122,480	[4]	0	[4]
Initial investment	78,129	[4]
Investment earnings, net of amortization	5,690	[4]		[4]
Contributions	38,661	[4]		[4]
Distributions		[4]		[4]
Distributions in excess of cumulative earnings		[4]
Balance	$ 0	[4]		[4]
Table Text Block Supplement [Abstract]
Approval Percentage	50.00%

[1] WES has a 14.81% interest in Fort Union, a joint venture which owns a gathering pipeline and treating facilities in the Powder River Basin. Anadarko is the construction manager and physical operator of the Fort Union facilities. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the owners’ firm gathering agreements, require 65% or unanimous approval of the owners.

[2] WES has a 10% interest in White Cliffs, a limited liability company which owns a crude oil pipeline that originates in Platteville, Colorado and terminates in Cushing, Oklahoma. The third-party majority owner is the manager of the White Cliffs operations. Certain business decisions, including, but not limited to, approval of annual budgets and decisions with respect to significant expenditures, contractual commitments, acquisitions, material financings, dispositions of assets or admitting new members, require more than 75% approval of the members.

[3] WES has a 22% interest in Rendezvous, a limited liability company that operates gas gathering facilities in Southwestern Wyoming. Certain business decisions, including, but not limited to, decisions with respect to significant expenditures or contractual commitments, annual budgets, material financings, dispositions of assets or amending the members’ gas servicing agreements, require unanimous approval of the members.

[4] WES has a 25% interest in the Mont Belvieu JV, an entity formed to design, construct, and own two fractionation trains located in Mont Belvieu, Texas. A third party is the operator of the Mont Belvieu JV fractionation trains. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the creation, appointment, or removal of officer positions require 50% or unanimous approval of the owners.