Derivative Instruments - Effect of Derivative Instruments - Statement of Income Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Derivative [Line Items]
Unrealized (gains) losses on derivatives, net	$ 377		$ 616		$ (114)
Total (gains) losses on derivatives, net	(326)		461		(608)
Gathering, Processing, and Marketing Sales and Gains (Losses) on Derivatives, Net [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	(685)		(147)		(495)
Unrealized (gains) losses on derivatives, net	377		616		(114)
Total (gains) losses on derivatives, net	(308)		469		(609)
Commodity Derivatives [Member] | Gathering, Processing, and Marketing Sales [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	2	[1]	20	[1]	3	[1]
Unrealized (gains) losses on derivatives, net	16	[1]	(12)	[1]	(4)	[1]
Total (gains) losses on derivatives, net	18	[1]	8	[1]	(1)	[1]
Commodity Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	(753)		(226)		(498)
Unrealized (gains) losses on derivatives, net	366		(336)		(395)
Total (gains) losses on derivatives, net	(387)		(562)		(893)
Interest-Rate and Other Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]
Derivative [Line Items]
Realized (gains) losses on derivatives, net	66	[2]	59	[2]
Unrealized (gains) losses on derivatives, net	(5)		964		285
Total (gains) losses on derivatives, net	$ 61		$ 1,023		$ 285

[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.