Noncontrolling Interests - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		1 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member]	Mar. 31, 2011 Western Gas Partners Limited Partnership [Member]	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member]	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member] Limited Partner [Member]	Sep. 30, 2011 Western Gas Partners Limited Partnership [Member] General Partner [Member]
Noncontrolling Interest [Line Items]
Common units issued to the public				6	4	6
Proceeds raised from offering by subsidiary		$ 328	$ 97	$ 198	$ 130
Amount of noncontrolling interests transferred to paid-in capital upon conversion of subordinated limited partner units to common units						162
Amount recorded to paid-in capital for change in ownership interest upon equity issuance						32
Anadarko's ownership interest in Western Gas Partners, LP							43.30%	2.00%
Net income (loss) attributable to common stockholders, including increases in paid-in-capital related to sale of subsidiary units and conversion of subordinated limited partner units to common units	$ (2,857)	$ (2,097)