Debt and Interest Expense - Debt Activity Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument, Increase (Decrease), Net [Abstract]
Carrying value, beginning balance	$ 13,269	$ 15,230
Debt Instrument [Line Items]
Repayments of Debt	(710)	(3,044)	(1,154)
Other, net	38	35
Carrying value, ending balance	13,557	13,269	15,230
6.125% Senior Notes due 2012
Debt Instrument [Line Items]
Repayments of Debt		(131)
Debt instrument, stated interest rate		6.125%
Debt instrument, maturity date		Mar. 15, 2012
5.000% Senior Notes due 2012
Debt Instrument [Line Items]
Repayments of Debt		(39)
Debt instrument, stated interest rate		5.00%
Debt instrument, maturity date		Oct. 01, 2012
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Repayments of credit facilities		(2,500)
Western Gas Partners, LP [Member] | WES 4.000% Senior Notes due 2022
Debt Instrument [Line Items]
Issuance		674
Debt instrument, stated interest rate	4.00%
Debt instrument, maturity date	Jun. 01, 2022
Western Gas Partners, LP [Member] | WES 2.600% Senior Notes due 2018
Debt Instrument [Line Items]
Issuance	250
Debt instrument, stated interest rate	2.60%
Debt instrument, maturity date	Aug. 15, 2018
Western Gas Partners, LP [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings	710	374
Repayments of credit facilities	$ (710)	$ (374)