Noncontrolling Interests (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Western Gas Equity Partners, LP [Member] Limited Partner [Member]	Sep. 30, 2014 Western Gas Partners, LP [Member] Continuous Offering Program [Member]	Mar. 31, 2014 Western Gas Partners, LP [Member] Option on Securities [Member]	Sep. 30, 2014 Western Gas Partners, LP [Member] Limited Partner [Member]	Sep. 30, 2014 Western Gas Partners, LP [Member] Limited Partner [Member] Western Gas Equity Partners, LP, Ownership Interest [Member]	Sep. 30, 2014 Western Gas Partners, LP [Member] Limited Partner [Member] Other Anadarko Subsidiaries, Ownership Interest [Member]	Sep. 30, 2014 Western Gas Partners, LP [Member] General Partner [Member] Western Gas Equity Partners, LP, Ownership Interest [Member]
Noncontrolling Interest [Line Items]
Units issued to the public			5,750,000	1,100,000	300,000
Net proceeds raised from offering	$ 434	$ 418	$ 335	$ 81	$ 18
Ownership interest in subsidiary			88.30%				40.60%	0.60%	2.00%
Public ownership interest in subsidiary			11.70%			56.80%