Debt and Interest Expense - Debt Activity Table (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]
Carrying value, beginning balance	$ 13,557
Debt Instrument [Line Items]
Other, net	28
Carrying value, ending balance	14,720
Senior Notes 1 [Member] | Western Gas Partners, LP [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Issuance	101
Debt instrument, stated interest rate	2.60%
Debt instrument, maturity date	Aug. 15, 2018
Senior Notes 2 [Member] | Western Gas Partners, LP [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Issuance	394
Debt instrument, stated interest rate	5.45%
Debt instrument, maturity date	Apr. 01, 2044
Senior Notes 3 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Issuance	624
Debt instrument, stated interest rate	3.45%
Debt instrument, maturity date	Jul. 15, 2024
Senior Notes 4 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Issuance	621
Debt instrument, stated interest rate	4.50%
Debt instrument, maturity date	Jul. 15, 2044
WES RCF [Member] | Western Gas Partners, LP [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings	650
Repayments	(480)
Senior Notes 5 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Repayments	(500)
Debt instrument, stated interest rate	7.625%
Debt instrument, maturity date	Mar. 15, 2014
Senior Notes 6 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Repayments	$ (275)
Debt instrument, stated interest rate	5.75%
Debt instrument, maturity date	Jun. 15, 2014