Asset Impairments (Details) (USD $) In Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Impaired Long-Lived Assets Held and Used [Line Items]
Total - Impairment of Oil and Gas Properties	$ 0	$ 100	[1]	$ 139	[1]	$ 100	[1]
East Texas [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total - Impairment of Oil and Gas Properties	0	0		116		0
Iron Horse [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total - Impairment of Oil and Gas Properties	0	71		15		71
New Albany Shale [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total - Impairment of Oil and Gas Properties	0	19		0		19
Other Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Total - Impairment of Oil and Gas Properties	$ 0	$ 10		$ 8		$ 10

[1] See Note 4. Asset Impairments.