Supplementary Oil and Gas Disclosure (Unaudited) - Changes in Standardized Measure (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Beginning of the Period	$ 5,833	$ 4,436	$ 5,981
Revision of Previous Estimates [Abstract]
Changes in Prices and Costs	(743)	979	(1,528)
Changes in Quantities	680	459	(404)
Changes in Future Development Costs	310	(259)	273
Development Costs Incurred During The Period	(857)	(758)	(594)
Additions to proved reserves resulting from extensions, discoveries and improved recovery, less related costs	860	1,061	815
Purchases and sales of reserves in place, net	(450)	13	(758)
Accretion of Discount	788	585	683
Sales of oil and gas, net of production costs	1,737	1,349	1,631
Net change in income taxes	(332)	(819)	773
Production timing and other	146	(31)	(362)
Net increase (decrease)	379	1,397	(1,545)
Ending Balance	6,212	5,833	4,436
Domestic [Member]
Beginning of the Period	4,628	3,408	4,724
Revision of Previous Estimates [Abstract]
Changes in Prices and Costs	(492)	944	(1,490)
Changes in Quantities	784	81	(427)
Changes in Future Development Costs	253	(83)	294
Development Costs Incurred During The Period	(698)	(549)	(434)
Additions to proved reserves resulting from extensions, discoveries and improved recovery, less related costs	860	1,012	791
Purchases and sales of reserves in place, net	(171)	13	(758)
Accretion of Discount	655	470	542
Sales of oil and gas, net of production costs	1,662	973	1,129
Net change in income taxes	(383)	(815)	650
Production timing and other	160	22	(223)
Net increase (decrease)	702	1,220	(1,316)
Ending Balance	5,330	4,628	3,408
Malaysia [Member]
Beginning of the Period	303	416	692
Revision of Previous Estimates [Abstract]
Changes in Prices and Costs	(132)	33	(14)
Changes in Quantities	0	76	23
Changes in Future Development Costs	129	(126)	(19)
Development Costs Incurred During The Period	(12)	(79)	(93)
Additions to proved reserves resulting from extensions, discoveries and improved recovery, less related costs	0	49	0
Purchases and sales of reserves in place, net	(279)	0	0
Accretion of Discount	19	33	64
Sales of oil and gas, net of production costs	54	330	439
Net change in income taxes	0	59	119
Production timing and other	2	14	(103)
Net increase (decrease)	(303)	(113)	(276)
Ending Balance	0	303	416
China [Member]
Beginning of the Period	902	612	565
Revision of Previous Estimates [Abstract]
Changes in Prices and Costs	(119)	2	(24)
Changes in Quantities	(104)	302	0
Changes in Future Development Costs	(72)	(50)	(2)
Development Costs Incurred During The Period	(147)	(130)	(67)
Additions to proved reserves resulting from extensions, discoveries and improved recovery, less related costs	0	0	24
Purchases and sales of reserves in place, net	0	0	0
Accretion of Discount	114	82	77
Sales of oil and gas, net of production costs	21	46	63
Net change in income taxes	51	(63)	4
Production timing and other	(16)	(67)	(36)
Net increase (decrease)	(20)	290	47
Ending Balance	$ 882	$ 902	$ 612