Debt and Interest Expense - Debt Outstanding Table (details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2013 Senior Notes 4 Percent Due 2022 [Member] Western Gas Partners [Member]		Dec. 31, 2012 Senior Notes 4 Percent Due 2022 [Member] Western Gas Partners [Member]		Oct. 31, 2012 Senior Notes 4 Percent Due 2022 [Member] Western Gas Partners [Member]	Jun. 30, 2012 Senior Notes 4 Percent Due 2022 [Member] Western Gas Partners [Member]	Mar. 31, 2013 Senior Notes 5 Point 375 Percent Due 2021 [Member] Western Gas Partners [Member]		Dec. 31, 2012 Senior Notes 5 Point 375 Percent Due 2021 [Member] Western Gas Partners [Member]		May 31, 2011 Senior Notes 5 Point 375 Percent Due 2021 [Member] Western Gas Partners [Member]	Mar. 31, 2013 Revolving Credit Facility [Member] Western Gas Partners [Member]
Debt Instrument Line Items
Principal	$ 1,555,000		$ 1,170,000		$ 670,000		$ 670,000		$ 150,000	$ 520,000	$ 500,000		$ 500,000		$ 500,000	$ 385,000
Carrying Value	1,553,319		1,168,278		673,533		673,617				494,786		494,661			385,000
Fair Value	$ 1,554,883	[1]	$ 1,169,874	[1]	$ 669,933	[1]	$ 669,928	[1]			$ 499,950	[1]	$ 499,946	[1]		$ 385,000	[1]

[1] Fair value is measured using Level 2 inputs.