Debt and Interest Expense - Additional Information (Detail) (USD $)							9 Months Ended				9 Months Ended		9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2013 Fair Value Inputs Level 1 and Level 2 [Member] Market Approach Valuation Technique [Member]	Dec. 31, 2012 Fair Value Inputs Level 1 and Level 2 [Member] Market Approach Valuation Technique [Member]	Sep. 30, 2013 Senior Notes 1 [Member]	Sep. 30, 2013 Senior Notes 2 [Member]	Sep. 30, 2013 Senior Notes Zero Coupon [Member]	Oct. 10, 2013 Senior Notes Zero Coupon [Member]	Sep. 30, 2013 Senior Notes 3 [Member] Western Gas Partners, LP [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility [Member] Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity												$ 5,000,000,000	$ 800,000,000
Debt instrument, principal amount	15,302,000,000			14,952,000,000			500,000,000	275,000,000			250,000,000
Debt instrument, stated interest rate							7.625%	5.75%			2.60%
Debt instrument, maturity date							Mar. 15, 2014	Jun. 15, 2014	Oct. 10, 2036		Aug. 15, 2018
Debt instrument, accreted value	13,647,000,000	13,538,000,000	13,663,000,000	13,269,000,000						718,000,000
Debt Instrument, earliest call date									Oct. 10, 2013
Estimated fair value of total borrowings					15,800,000,000	16,200,000,000
Line of credit, expiration date													Mar. 24, 2016
Line of credit, outstanding borrowings													100,000,000
Line of credit, interest rate													1.68%
Line of credit, available borrowing capacity													687,000,000
Outstanding letters of credit													$ 13,000,000