Asset Impairments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					12 Months Ended
	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments	$ 620	$ 131	$ 8	$ 44	$ 100	$ 759	$ 144	$ 604
Piceance (onshore US) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						487	0	0
Tri-State (onshore US) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						121	0	0
Iron Horse [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						15	89	0
East Texas [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						128	0	0
New Albany Shale [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	19	44
Granite Wash (onshore US) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	0	389
Main Pass (Gulf of Mexico Shelf) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	5	48
Raton (Deepwater Gulf of Mexico) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	6	23
Noa/Noa South (Isreal) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	25	0
Ecuador [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						0	0	100
Other Onshore US Proved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						6	0	0
Other Offshore International Proved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total asset impairments						$ 2	$ 0	$ 0