Asset Impairments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	$ 104	$ 757	$ 144
Piceance (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	39	487	0
South Raton (Deepwater Gulf of Mexico)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	34	0	0
Mari-B, Noa, Pinnacles (Offshore Israel)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	31	0	0
East Texas (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	128	0
Tri-State (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	121	0
Iron Horse (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	15	89
Other Onshore US Properties
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	6	0
New Albany Shale (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	0	19
Noa/Noa South (Offshore Israel)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	0	25
Raton (Deepwater Gulf of Mexico)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	0	0	6
Main Pass (Gulf of Mexico Shelf)
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of Oil and Gas Properties	$ 0	$ 0	$ 5