Derivative Instruments - Effect of Derivative Instruments - Statement of Income 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
Derivative [Line Items]
Realized (gains) losses on derivatives, net	$ (197)		$ (70)		$ (598)		$ (136)
Unrealized (gains) losses on derivatives, net	456		692		539		767
Derivative (gain) loss, net	259		622		(59)		631
Commodity Contract [Member] | Gathering, Processing, and Marketing Sales [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	3	[1]	1	[1]			17	[1]
Unrealized (gains) losses on derivatives, net	5	[1]	(3)	[1]	18	[1]	(8)	[1]
Derivative (gain) loss, net	8	[1]	(2)	[1]	18	[1]	9	[1]
Commodity Contract [Member] | (Gains) Losses on Commodity Derivatives, net [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	(200)		(71)		(600)		(155)
Unrealized (gains) losses on derivatives, net	437		(159)		369		(162)
Derivative (gain) loss, net	237		(230)		(231)		(317)
Interest Rate Contract and Other [Member] | (Gains) Losses on Other Derivatives, net [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net					2	[2]	2	[2]
Unrealized (gains) losses on derivatives, net	14		854		152		937
Derivative (gain) loss, net	$ 14		$ 854		$ 154		$ 939

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

[2] In the first quarter of 2012, the Company revised the definition of Adjusted EBITDAX to exclude Algeria exceptional profits tax settlement, Tronox-related contingent loss, and realized (gains) losses on other derivatives, net. Prior periods have been adjusted to reflect this change.