Equity Investments - Equity Investments Table (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	[3]	Sep. 30, 2016		Sep. 30, 2015	[3]
Schedule of Equity Method Investments [Line Items]
Balance	[1]				$ 618,887
Investment earnings (loss), net of amortization	[2]	$ 20,294	$ 21,976		56,801		$ 59,137
Contributions					(139)		9,052
Distributions					(59,671)		(60,645)
Distributions in excess of cumulative earnings					(16,592)	[4]	$ (12,409)
Balance		599,286			599,286
Western Gas Partners, LP [Member] | Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance					17,122
Investment earnings (loss), net of amortization					(308)
Contributions					0
Distributions					(787)
Distributions in excess of cumulative earnings	[4]				(3,354)
Balance		12,673			12,673
Western Gas Partners, LP [Member] | White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance					50,439
Investment earnings (loss), net of amortization					10,474
Contributions					441
Distributions					(10,038)
Distributions in excess of cumulative earnings	[4]				(3,393)
Balance		47,923			47,923
Western Gas Partners, LP [Member] | Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance					50,913
Investment earnings (loss), net of amortization					1,413
Contributions					0
Distributions					(2,573)
Distributions in excess of cumulative earnings	[4]				(1,541)
Balance		48,212			48,212
Western Gas Partners, LP [Member] | Mont Belvieu JV [Member]
Schedule of Equity Method Investments [Line Items]
Balance					117,089
Investment earnings (loss), net of amortization					18,245
Contributions					0
Distributions					(18,274)
Distributions in excess of cumulative earnings	[4]				(3,963)
Balance		113,097			113,097
Western Gas Partners, LP [Member] | Texas Express Gathering LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance					16,283
Investment earnings (loss), net of amortization					529
Contributions					0
Distributions					(546)
Distributions in excess of cumulative earnings	[4]				(266)
Balance		16,000			16,000
Western Gas Partners, LP [Member] | Texas Express Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance					194,803
Investment earnings (loss), net of amortization					12,239
Contributions					(580)
Distributions					(12,427)
Distributions in excess of cumulative earnings	[4]				(3,720)
Balance		190,315			190,315
Western Gas Partners, LP [Member] | Front Range Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance					172,238
Investment earnings (loss), net of amortization					14,209
Contributions					0
Distributions					(15,026)
Distributions in excess of cumulative earnings	[4]				(355)
Balance		$ 171,066			$ 171,066

[1] Financial information has been recast to include the financial position and results attributable to the Springfield interest. See Note 1 and Note 2.

[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] Financial information has been recast to include the financial position and results attributable to the Springfield interest. See Note 1 and Note 2.

[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.