Transactions with Affiliates - Gains (Losses) on Commodity Price Swap Agreements Table (Details) - Western Gas Partners, LP [Member] - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements		$ 15,522	$ 6,383	$ 55,678	$ 30,190
Sales [Member]
Gains (losses) on commodity price swap agreements related to sales and purchases
Net gains (losses) on commodity price swap agreements	[1]	39,520	25,916	155,575	68,271
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]	5,774	3,179	39,100	1,525
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]	33,746	22,737	116,475	66,746
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]	$ (23,998)	$ (19,533)	$ (99,897)	$ (38,081)

[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.