Impairment Table (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	$ 85	$ 38	$ 343	$ 281
Land and Building [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	8	7	247	227
Exploration and Production Equipment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	24	31	27	54
Gas Gathering and Processing Equipment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	21	0	22	0
Other Assets
Impaired Long-Lived Assets Held and Used [Line Items]
Impairments of fixed assets and other	$ 32	$ 0	$ 47	$ 0