Consolidated Statement of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.80	$ (6.70)	$ 3.00
Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share	$ 0.14	$ (2.10)	$ 1.03
Earnings (Loss) Per Share, Basic	$ 0.94	$ (8.80)	$ 4.03
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.80	$ (6.70)	$ 2.97
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.14	$ (2.10)	$ 1.02
Earnings (Loss) Per Share, Diluted	$ 0.94	$ (8.80)	$ 3.99
Operating expenses:
Depreciation, depletion and amortization	$ 930	$ 955	$ 767
Ceiling test impairment	0	1,488	0
Income tax provision (benefit):
Current	(4)	2	17
Deferred	66	(513)	201
Total income tax provision (benefit)	62	(511)	218
Income (Loss) from Continuing Operations Attributable to Parent	108	(902)	401
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	39	(282)	138
Net income (loss)	147	(1,184)	539
Other income (expenses):
Interest expense	(205)	(205)	(175)
Interest Costs Capitalized Adjustment	53	68	82
Commodity derivative income (expense)	(97)	120	195
Other	0	(2)	2
Total other income (expenses)	(249)	(19)	104
Income (loss) before income taxes	170	(1,413)	619
Weighted-average number of shares outstanding for basic earnings (loss) per share	135	135	134
Weighted average number of shares outstanding for diluted earnings (loss) per share	136	135	135
Continuing Operations [Member]
Statement [Line Items]
Oil, gas and NGL revenues	1,789	1,476	1,742
Operating expenses:
Lease operating	413	406	358
Production and other taxes	67	67	68
Depreciation, depletion and amortization	668	683	621
General and administrative	219	211	180
Ceiling test impairment	0	1,488	0
Other	3	15	0
Total operating expenses	1,370	2,870	1,227
Income (loss) from operations	$ 419	$ (1,394)	$ 515