Supplementary Oil and Gas Disclosure (Unaudited) - Costs Incurred (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Costs Incurred, Acquisition of Oil and Gas Properties [Abstract]
Costs Incurred, Acquisition of Unproved Oil and Gas Properties	$ 146	$ 154	$ 64
Costs Incurred, Acquisition of Oil and Gas Properties with Proved Reserves	6	9	3
Costs Incurred, Exploration Costs	1,089	1,100	993
Costs Incurred, Development Costs	942	1,042	853
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities Total	2,183	2,305	1,913
Domestic [Member]
Costs Incurred, Acquisition of Oil and Gas Properties [Abstract]
Costs Incurred, Acquisition of Unproved Oil and Gas Properties	146	154	64
Costs Incurred, Acquisition of Oil and Gas Properties with Proved Reserves	6	8	3
Costs Incurred, Exploration Costs	1,089	966	929
Costs Incurred, Development Costs	772	691	659
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities Total	2,013	1,819	1,655
Malaysia [Member]
Costs Incurred, Acquisition of Oil and Gas Properties [Abstract]
Costs Incurred, Acquisition of Unproved Oil and Gas Properties	0	0	0
Costs Incurred, Acquisition of Oil and Gas Properties with Proved Reserves	0	0	0
Costs Incurred, Exploration Costs	0	101	63
Costs Incurred, Development Costs	14	211	108
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities Total	14	312	171
China [Member]
Costs Incurred, Acquisition of Oil and Gas Properties [Abstract]
Costs Incurred, Acquisition of Unproved Oil and Gas Properties	0	0	0
Costs Incurred, Acquisition of Oil and Gas Properties with Proved Reserves	0	1	0
Costs Incurred, Exploration Costs	0	33	1
Costs Incurred, Development Costs	156	140	86
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities Total	$ 156	$ 174	$ 87