Consolidated Statements Of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenues and other income:
Oil and gas	$ 517	$ 890
Sales of purchased oil and gas	103	147
Interest and other	6	5
Derivative gains (losses), net	241	(104)
Gain (loss) on disposition of assets, net	1	6
Total revenues and other income	868	944
Costs and expenses:
Oil and gas production	180	158
Production and ad valorem taxes	39	55
Depletion, depreciation and amortization	310	217
Purchased oil and gas	108	143
Impairment of oil and gas properties	138	0
Exploration and abandonments	25	31
General and administrative	82	81
Accretion of discount on asset retirement obligations	3	3
Interest	46	45
Other	48	15
Costs and Expenses	979	748
Income (loss) from continuing operations before income taxes	(111)	196
Income tax benefit (provision)	37	(51)
Income (loss) from continuing operations	(74)	145
Loss from discontinued operations, net of tax	(4)	(22)
Net income (loss)	(78)	123
Net income (loss) attributable to common stockholders	(78)	123
Basic earnings per share:
Income (loss) from continuing operations	$ (0.50)	$ 1.00
Loss from discontinued operations	$ (0.02)	$ (0.15)
Net income (loss)	$ (0.52)	$ 0.85
Diluted earnings per share:
Income (loss) from continuing operations	$ (0.50)	$ 1.00
Loss from discontinued operations	$ (0.02)	$ (0.15)
Net income (loss)	$ (0.52)	$ 0.85
Weighted average shares outstanding:
Basic	149	143
Diluted	149	143
Dividends declared per share	$ 0.04	$ 0.04
Amounts attributable to common stockholders:
Net income (loss) attributable to common stockholders	$ (78)	$ 123