Supplementary Oil and Gas Disclosure (Unaudited) - Capitalized Costs (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	$ 15,707	$ 15,176
Capitalized Costs, Unproved Properties	677	1,231
Gross oil and gas properties	16,384	16,407
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(8,152)	(8,306)
Net oil and gas properties	8,232	8,101
Domestic [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	14,998	13,185
Capitalized Costs, Unproved Properties	677	1,116
Gross oil and gas properties	15,675	14,301
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(8,022)	(7,185)
Net oil and gas properties	7,653	7,116
Malaysia [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	0	1,441
Capitalized Costs, Unproved Properties	0	115
Gross oil and gas properties	0	1,556
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	0	(1,009)
Net oil and gas properties	0	547
China [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	709	550
Capitalized Costs, Unproved Properties	0	0
Gross oil and gas properties	709	550
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(130)	(112)
Net oil and gas properties	$ 579	$ 438