Transactions With Affiliates - Gains Losses Commodity Price Swap Agreements Table (details) (Western Gas Partners [Member], USD $) In Thousands, unless otherwise specified	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	55,414	[1]	5,788	[1]
Sales [Member] | Natural Gas [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	10,982	[1]	(3,667)	[1]
Sales [Member] | Natural Gas Liquids [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	44,432	[1]	9,455	[1]
Cost of Sales [Member]
Gains (losses) on commodity price swap
Net gains (losses) on commodity price swap agreements	$ (34,179)	[2]	$ (19)	[2]

[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.