Equity Investments - Equity Investments Table (details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Balance	$ 593,400		$ 219,766
Initial investment			78,129
Investment earnings (loss), net of amortization	57,836	[1],[2],[3]	22,948	[1],[2],[3]	16,042	[1],[2],[3]
Contributions	64,278		294,693		108,457
Capitalized interest	857		17,033
Distributions	(62,967)	[3]	(17,698)	[3]	(20,660)	[3]
Distributions in excess of cumulative earnings	(18,055)	[3],[4]	(4,438)	[3],[4]	0	[3]
Balance	634,492		593,400		219,766
Equity Investments [Member]
Schedule of Equity Method Investments [Line Items]
Contributions	63,421		277,660
Western Gas Partners [Member] | Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance	25,172	[5]	23,453	[5]
Initial investment			0	[5]
Investment earnings (loss), net of amortization	6,344	[5]	6,273	[5]
Contributions	0	[5]	16	[5]
Capitalized interest	0	[5]	0	[5]
Distributions	(5,583)	[5]	(4,570)	[5]
Distributions in excess of cumulative earnings	0	[4],[5]	0	[4],[5]
Balance	25,933	[5]	25,172	[5]
Table Text Block Supplement [Abstract]
Equity investment ownership	14.81%
Approval percentage	65.00%
Western Gas Partners [Member] | White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance	35,039	[6]	17,567	[6]
Initial investment			0	[6]
Investment earnings (loss), net of amortization	11,912	[6]	9,681	[6]
Contributions	10,456	[6]	19,087	[6]
Capitalized interest	0	[6]	0	[6]
Distributions	(11,330)	[6]	(9,099)	[6]
Distributions in excess of cumulative earnings	(1,762)	[4],[6]	(2,197)	[4],[6]
Balance	44,315	[6]	35,039	[6]
Table Text Block Supplement [Abstract]
Equity investment ownership	10.00%
Approval percentage	75.00%
Western Gas Partners [Member] | Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance	60,928	[7]	65,110	[7]
Initial investment			0	[7]
Investment earnings (loss), net of amortization	1,729	[7]	2,088	[7]
Contributions	0	[7]	0	[7]
Capitalized interest	0	[7]	0	[7]
Distributions	(3,669)	[7]	(4,029)	[7]
Distributions in excess of cumulative earnings	(2,652)	[4],[7]	(2,241)	[4],[7]
Balance	56,336	[7]	60,928	[7]
Table Text Block Supplement [Abstract]
Equity investment ownership	22.00%
Approval percentage	100.00%
Western Gas Partners [Member] | Mont Belvieu Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Balance	122,480	[8]	0	[8]
Initial investment			78,129	[8]
Investment earnings (loss), net of amortization	29,029	[8]	5,690	[8]
Contributions	3,957	[8]	37,309	[8]
Capitalized interest	0	[8]	1,352	[8]
Distributions	(34,129)	[8]	0	[8]
Distributions in excess of cumulative earnings	0	[4],[8]	0	[4],[8]
Balance	121,337	[8]	122,480	[8]
Table Text Block Supplement [Abstract]
Equity investment ownership	25.00%
Approval percentage	50.00%
Western Gas Partners [Member] | Mont Belvieu Joint Venture [Member] | Fractionation Train [Member]
Table Text Block Supplement [Abstract]
Assets, number of units	2
Western Gas Partners [Member] | Texas Express Gathering Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	16,649	[9]	9,033	[9]
Initial investment			0	[9]
Investment earnings (loss), net of amortization	650	[9]	93	[9]
Contributions	352	[9]	6,732	[9]
Capitalized interest	0	[9]	791	[9]
Distributions	(523)	[9]	0	[9]
Distributions in excess of cumulative earnings	(338)	[4],[9]	0	[4],[9]
Balance	16,790	[9]	16,649	[9]
Table Text Block Supplement [Abstract]
Equity investment ownership	20.00%
Approval percentage	50.00%
Western Gas Partners [Member] | Texas Express Gathering Limited Liability Company [Member] | Natural Gas Liquids Gathering System [Member]
Table Text Block Supplement [Abstract]
Assets, number of units	2
Western Gas Partners [Member] | Texas Express Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	197,731	[10]	80,737	[10]
Initial investment			0	[10]
Investment earnings (loss), net of amortization	6,108	[10]	(776)	[10]
Contributions	6,623	[10]	108,969	[10]
Capitalized interest	0	[10]	8,801	[10]
Distributions	(5,622)	[10]	0	[10]
Distributions in excess of cumulative earnings	(6,047)	[10],[4]	0	[10],[4]
Balance	198,793	[10]	197,731	[10]
Table Text Block Supplement [Abstract]
Equity investment ownership	20.00%
Approval percentage	50.00%
Western Gas Partners [Member] | Front Range Pipeline Limited Liability Company [Member]
Schedule of Equity Method Investments [Line Items]
Balance	135,401	[11]	23,866	[11]
Initial investment			0	[11]
Investment earnings (loss), net of amortization	2,064	[11]	(101)	[11]
Contributions	42,033	[11]	105,547	[11]
Capitalized interest	857	[11]	6,089	[11]
Distributions	(2,111)	[11]	0	[11]
Distributions in excess of cumulative earnings	(7,256)	[11],[4]	0	[11],[4]
Balance	$ 170,988	[11]	$ 135,401	[11]
Table Text Block Supplement [Abstract]
Equity investment ownership	33.33%
Approval percentage	50.00%

[1] Income earned from equity investments is classified as affiliate. See Note 1.

[2] Represents amounts earned or incurred on and subsequent to the date of acquisition of WES assets, as well as amounts earned or incurred by Anadarko on a historical basis related to WES assets prior to the acquisition of such assets by WES, recognized under gathering, treating or processing agreements, and purchase and sale agreements.

[3] Income earned on, distributions from and contributions to equity investments are classified as affiliate. See Note 1.

[4] Distributions in excess of cumulative earnings, classified as investing cash flows in the consolidated statements of cash flows, is calculated on an individual investment basis.

[5] WES has a 14.81% interest in Fort Union, a joint venture that 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.

[6] WES has a 10% interest in White Cliffs, a limited liability company that 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.

[7] 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.

[8] 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.

[9] WES has a 20% interest in TEG, an entity that consists of two NGL gathering systems that link natural gas processing plants to TEP. Enbridge Midcoast Energy, LP (“Enbridge”) is the operator of the two gathering systems. Certain business decisions, including, but not limited to, decisions with respect to the execution of contracts, settlements, disposition of assets, or the delegation, creation, appointment, or removal of officer positions require more than 50% approval of the members.

[10] WES has a 20% interest in TEP, which consists of an NGL pipeline that originates in Skellytown, Texas and extends to Mont Belvieu, Texas. Enterprise Products Operating LLC (“Enterprise”) is the operator of TEP. 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 more than 50% approval of the members.

[11] WES has a 33.33% interest in the FRP, an NGL pipeline that extends from Weld County, Colorado to Skellytown, Texas. Enterprise is the operator of FRP. 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 more than 50% approval of the members.