Quarterly Results of Operations (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Ceiling test impairment					$ 1,500				$ 0	$ 1,488	$ 0
Income (Loss) from Continuing Operations Attributable to Parent	31	(4)	106	(25)	(923)	(82)	64	39	108	(902)	401
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(14)	31	5	17	(479)	49	71	77	39	(282)	138
Net Income (Loss) Attributable to Parent	17	27	111	(8)	(1,402)	(33)	135	116	147	(1,184)	539
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.23	$ (0.03)	$ 0.78	$ (0.19)	$ (6.86)	$ (0.61)	$ 0.47	$ 0.29	$ 0.80	$ (6.70)	$ 3.00
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ (0.10)	$ 0.08	$ 0.04	$ 0.13	$ (3.53)	$ 0.37	$ 0.53	$ 0.57	$ 0.14	$ (2.10)	$ 1.03
Earnings (Loss) Per Share, Basic	$ 0.13	$ 0.05	$ 0.82	$ (0.06)	$ (10.39)	$ (0.24)	$ 1.00	$ 0.86	$ 0.94	$ (8.80)	$ 4.03
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.23	$ (0.03)	$ 0.78	$ (0.19)	$ (6.86)	$ (0.61)	$ 0.47	$ 0.29	$ 0.80	$ (6.70)	$ 2.97
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ (0.10)	$ 0.08	$ 0.04	$ 0.13	$ (3.53)	$ 0.37	$ 0.53	$ 0.57	$ 0.14	$ (2.10)	$ 1.02
Earnings (Loss) Per Share, Diluted	$ 0.13	$ 0.05	$ 0.82	$ (0.06)	$ (10.39)	$ (0.24)	$ 1.00	$ 0.86	$ 0.94	$ (8.80)	$ 3.99
Continuing Operations [Member]
Oil and Gas Revenue	498	486	435	370	352	371	350	403	1,789	1,476	1,742
Ceiling test impairment									0	1,488	0
Income (loss) from operations	$ 121	$ 131	$ 89	$ 78	$ (1,483)	$ 19	$ 1	$ 69	$ 419	$ (1,394)	$ 515