Transactions With Affiliates - Gains Losses Commodity Price Swap Agreements Table (details) - Western Gas Partners [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2015	Mar. 31, 2014
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements		$ 21,235	$ 5,769
Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	[1]	55,414	5,788
Sales [Member] | Natural Gas [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	[1]	10,982	(3,667)
Sales [Member] | Natural Gas Liquids [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	[1]	44,432	9,455
Cost of Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	[2]	$ (34,179)	$ (19)

[1] Reported in affiliate natural gas, natural gas liquids and drip condensate sales in the consolidated statements of income in the period in which the related sale is recorded.

[2] Reported in cost of product in the consolidated statements of income in the period in which the related purchase is recorded.