Supplementary Oil and Gas Disclosure (Unaudited) - Capitalized Costs (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	$ 15,176	$ 12,736
Capitalized Costs, Unproved Properties	1,231	1,396
Gross oil and gas properties	16,407	14,132
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(8,306)	(7,378)
Net oil and gas properties	8,101	6,754
Domestic [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	13,185	11,221
Capitalized Costs, Unproved Properties	1,116	1,291
Gross oil and gas properties	14,301	12,512
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(7,185)	(6,535)
Net oil and gas properties	7,116	5,977
Malaysia [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	1,441	1,140
Capitalized Costs, Unproved Properties	115	104
Gross oil and gas properties	1,556	1,244
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(1,009)	(747)
Net oil and gas properties	547	497
China [Member]
Capitalized Costs, Oil and Gas Producing Activities, Gross [Abstract]
Capitalized Costs, Proved Properties	550	375
Capitalized Costs, Unproved Properties	0	1
Gross oil and gas properties	550	376
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities	(112)	(96)
Net oil and gas properties	$ 438	$ 280