Equity Investments - Equity Investments Table (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016
Schedule of Equity Method Investments [Line Items]
Balance		$ 594,208
Investment earnings (loss), net of amortization	[1]	19,461		$ 16,814
Distributions		(19,114)		(19,855)
Distributions in excess of cumulative earnings		(3,453)	[2]	$ (4,784)
Balance		591,102
Western Gas Partners, LP [Member] | Fort Union [Member]
Schedule of Equity Method Investments [Line Items]
Balance		12,833
Investment earnings (loss), net of amortization		805
Distributions		(845)
Distributions in excess of cumulative earnings	[2]	0
Balance		12,793
Western Gas Partners, LP [Member] | White Cliffs [Member]
Schedule of Equity Method Investments [Line Items]
Balance		47,319
Investment earnings (loss), net of amortization		3,098
Distributions		(2,952)
Distributions in excess of cumulative earnings	[2]	(615)
Balance		46,850
Western Gas Partners, LP [Member] | Rendezvous [Member]
Schedule of Equity Method Investments [Line Items]
Balance		46,739
Investment earnings (loss), net of amortization		249
Distributions		(734)
Distributions in excess of cumulative earnings	[2]	(809)
Balance		45,445
Western Gas Partners, LP [Member] | Mont Belvieu JV [Member]
Schedule of Equity Method Investments [Line Items]
Balance		112,805
Investment earnings (loss), net of amortization		6,863
Distributions		(6,125)
Distributions in excess of cumulative earnings	[2]	0
Balance		113,543
Western Gas Partners, LP [Member] | Texas Express Gathering LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance		15,846
Investment earnings (loss), net of amortization		367
Distributions		(272)
Distributions in excess of cumulative earnings	[2]	0
Balance		15,941
Western Gas Partners, LP [Member] | Texas Express Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance		189,194
Investment earnings (loss), net of amortization		4,276
Distributions		(4,339)
Distributions in excess of cumulative earnings	[2]	(851)
Balance		188,280
Western Gas Partners, LP [Member] | Front Range Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Balance		169,472
Investment earnings (loss), net of amortization		3,803
Distributions		(3,847)
Distributions in excess of cumulative earnings	[2]	(1,178)
Balance		$ 168,250

[1] Represents amounts earned or incurred on and subsequent to the date of the 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.

[2] 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.