Asset Impairments Impaired Long-Lived Assets Held and Used- text (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Sep. 30, 2014
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	$ 500	$ 86	$ 104
United States [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	250
South Raton (Deepwater Gulf of Mexico) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments				74
Other Deepwater Gulf of Mexico [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	51
Other (Onshore US) [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments					$ 31