Transactions with Affiliates - Gains Losses Commodity Price Swap Agreements Table (Details) - Western Gas Partners, LP [Member] - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements		$ 18,921	$ 18,038	$ 40,156	$ 23,807
Sales [Member]
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements	[1]	60,641	36,567	116,055	42,355
Sales [Member] | Natural Gas [Member]
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements	[1]	22,344	2,013	33,326	(1,654)
Sales [Member] | Natural Gas Liquids [Member]
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements	[1]	38,297	34,554	82,729	44,009
Cost of Sales [Member]
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements	[2]	$ (41,720)	$ (18,529)	$ (75,899)	$ (18,548)

[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.