Segment Information - Selected Financial Information for Anadarko's Reporting Segments Table (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Sales revenues	$ 3,283		$ 3,384		$ 9,895		$ 10,342
Gains (losses) on divestitures and other, net	49		(185)		106		(214)
Total	3,332		3,199		10,001		10,128
Operating costs and expenses	1,225	[1]	1,361	[1]	3,780	[1]	3,869	[1]
Realized (gains) losses on derivatives, net	(197)		(70)		(598)		(136)
Other (income) expense, net	(10)		40		(264)		(2)
Net income attributable to noncontrolling interests	21		23		67		62
Total expenses and other	1,036		1,353		3,233		3,774
Unrealized (gains) losses on derivatives, net included in marketing revenue	456		692		539		767
Adjusted EBITDAX	2,301		1,843		6,786		6,346
Excluding Tronox Related Contingent Loss [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	(10)	[2]	40	[2]	(14)	[2]	(2)	[2]
Gathering, Processing, and Marketing Sales [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Realized (gains) losses on derivatives, net	3	[3]	1	[3]			17	[3]
Unrealized (gains) losses on derivatives, net included in marketing revenue	5	[3]	(3)	[3]	18	[3]	(8)	[3]
(Gains) Losses on Commodity Derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Realized (gains) losses on derivatives, net	(200)		(71)		(600)		(155)
Unrealized (gains) losses on derivatives, net included in marketing revenue	437		(159)		369		(162)
Oil and Gas Exploration and Production Reporting Segment [Member]
Segment Reporting Information [Line Items]
Sales revenues	1,393		1,801		5,180		5,668
Intersegment revenues	1,587		1,244		3,796		3,699
Gains (losses) on divestitures and other, net	12		(193)		(17)		(307)
Total	2,992		2,852		8,959		9,060
Operating costs and expenses	840	[1]	955	[1]	2,639	[1]	2,717	[1]
Total expenses and other	840		955		2,639		2,717
Adjusted EBITDAX	2,152		1,897		6,320		6,343
Midstream Reporting Segment [Member]
Segment Reporting Information [Line Items]
Sales revenues	80		76		248		238
Intersegment revenues	232		251		701		684
Gains (losses) on divestitures and other, net	(6)		(31)		(8)		(11)
Total	306		296		941		911
Operating costs and expenses	182	[1]	210	[1]	545	[1]	575	[1]
Net income attributable to noncontrolling interests	21		23		67		62
Total expenses and other	203		233		612		637
Adjusted EBITDAX	103		63		329		274
Marketing Reporting Segment [Member]
Segment Reporting Information [Line Items]
Sales revenues	1,810		1,507		4,467		4,436
Intersegment revenues	(1,682)		(1,386)		(4,101)		(4,066)
Total	128		121		366		370
Operating costs and expenses	152	[1]	143	[1]	464	[1]	414	[1]
Total expenses and other	152		143		464		414
Adjusted EBITDAX	(19)		(25)		(80)		(52)
Marketing Reporting Segment [Member] | Gathering, Processing, and Marketing Sales [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Unrealized (gains) losses on derivatives, net included in marketing revenue	5		(3)		18		(8)
Other And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment revenues	(137)		(109)		(396)		(317)
Gains (losses) on divestitures and other, net	43		39		131		104
Total	(94)		(70)		(265)		(213)
Operating costs and expenses	51	[1]	53	[1]	132	[1]	163	[1]
Total expenses and other	(159)		22		(482)		6
Adjusted EBITDAX	65		(92)		217		(219)
Other And Intersegment Eliminations [Member] | Excluding Tronox Related Contingent Loss [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	(10)	[2]	40	[2]	(14)	[2]	(2)	[2]
Other And Intersegment Eliminations [Member] | (Gains) Losses on Commodity Derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Realized (gains) losses on derivatives, net	$ (200)		$ (71)		$ (600)		$ (155)

[1] Operating costs and expenses excludes exploration expense; depreciation, depletion, and amortization; impairments; Deepwater Horizon settlement and related costs; and Algeria exceptional profits tax settlement since these expenses are excluded from Adjusted EBITDAX.

[2] Other (income) expense, net excludes Tronox-related contingent loss since this expense is excluded from Adjusted EBITDAX.

[3] Represents the effect of marketing and trading derivative activities.