Capital Stock - Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss from continuing operations attributable to common shareholders									$ (1,372)	$ (10,844)	[1]	$ (6,653)	[1]
Net income (loss) from discontinued operations									(33)	492	[1],[2]	(1,707)	[1],[2]
Net income (loss) attributable to common shareholders	$ (182)	$ (607)	$ (244)	$ (372)	$ (4,015)	$ (4,143)	$ (860)	$ (1,334)	$ (1,405)	$ (10,352)	[1]	$ (8,360)	[1]
Income (loss) from continuing operations, shares									379	378		384
Income (loss) from discontinued operations, shares									379	378		384
Income (loss) attributable to common stock, shares									379	378	[1]	384	[1]
Basic and diluted net loss from continuing operations per share	$ (0.48)	$ (1.51)	$ (0.65)	$ (0.98)	$ (12.28)	$ (10.91)	$ (2.60)	$ (2.91)	$ (3.62)	$ (28.70)	[1]	$ (17.32)	[1]
Basic and diluted net loss from discontinued operations per share	0.00	(0.09)	0.00	0.00	1.66	(0.04)	0.32	(0.63)	(0.09)	1.30	[1]	(4.44)	[1]
Basic and diluted net loss per share	$ (0.48)	$ (1.60)	$ (0.65)	$ (0.98)	$ (10.62)	$ (10.95)	$ (2.28)	$ (3.54)	$ (3.71)	$ (27.40)	[1]	$ (21.76)	[1]

[1] Financial information for 2015 and 2014 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.

[2] Financial information for 2015 and 2014 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.