Fair Value Measurements (Details 2-Nonrecurring) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended
	Dec. 31, 2013 Assets Held and Used Eq Guinea Lng [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Ozona [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Ozona [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Powder River Basin [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Powder River Basin [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Droshky [Member]	Dec. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Assets Held and Used Eq Guinea Lng [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Financial Statement [Line Items]
Property, Plant, and Equipment, Fair Value Disclosure		$ 5	$ 16	$ 226					$ 226
Assets, Fair Value Adjustment		96	371	285	(21)	289	15	73	273	40
Fair Value of Intangible Assets, year-to-date		0	0	0
Impairment of Intangible Assets, Finite-lived		0	0	25
Equity Method Investment, Other than Temporary Impairment	$ 4