SUPPLEMENTAL QUARTERLY FINANCIAL DATA (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Oil and gas production revenues	$ 1,640	$ 1,389	$ 1,346	$ 1,512	$ 1,455	$ 1,439	$ 1,386	$ 1,087
Gain (loss) on divestitures	11	296	(21)	341	0	5	17	(1)	$ 627	$ 21	$ 281
Net income (loss)	518	105	613	267	(143)	(559)	(200)	(371)	1,503	(1,273)	(10,667)
Net income (loss) attributable to common stock	$ 456	$ 63	$ 572	$ 213	$ (182)	$ (607)	$ (244)	$ (372)	$ 1,304	$ (1,405)	$ (10,352)
Basic and diluted net loss per common share:
Basic net income (loss) per share (in USD per share)	$ 1.20	$ 0.16	$ 1.50	$ 0.56					$ 3.42	$ (3.71)	$ (27.40)
Diluted net income (loss) per share (in USD per share)	$ 1.19	$ 0.16	$ 1.50	$ 0.56					$ 3.41	$ (3.71)	$ (27.40)
Basic and diluted net loss per share (in USD per share)					$ (0.48)	$ (1.60)	$ (0.65)	$ (0.98)
Asset impairments	$ 32	$ 160	$ 39	$ 23	$ 144	$ 951	$ 238	$ 42	$ 8	$ 1,103	$ 9,472