Consolidated Statement of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Oil, gas and NGL revenues	$ 417	$ 284
Operating expenses:
Lease operating	56	61
Transportation and processing	72	63
Production and other taxes	14	10
Depreciation, depletion and amortization	106	177
General and administrative	47	44
Ceiling test and other impairments	0	506
Other	1	1
Total operating expenses	296	862
Income (loss) from operations	121	(578)
Other income (expense):
Interest expense	(38)	(41)
Capitalized interest	16	9
Commodity derivative income (expense)	(53)	17
Other, net	2	1
Total other income (expense)	33	(48)
Income (loss) before income taxes	154	(626)
Income tax provision (benefit):
Current	(2)	(2)
Deferred	9	0
Total income tax provision (benefit)	7	(2)
Net income (loss)	$ 147	$ (624)
Earnings Per Share [Abstract]
Basic	$ 0.74	$ (3.52)
Diluted	$ 0.73	$ (3.52)
Weighted-average number of shares outstanding for basic earnings (loss) per share	199	177
Weighted-average number of shares outstanding for diluted earnings (loss) per share	200	177
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 0	$ 0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 147	$ (624)