Asset Impairments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
South Raton (Deepwater Gulf of Mexico)	$ 34		$ 0		$ 34		$ 0
Piceance (Onshore US)	39		0		39		0
East Texas (Onshore US)	0		116		0		116
Other (Onshore US)	0		15		0		21
Total Asset Impairment Charges	$ 73	[1]	$ 131	[1]	$ 73	[1]	$ 137	[1]

[1] See Note 4. Asset Impairments.