Capital Stock - Net Income (loss) Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Basic:
Income (loss) attributable to common stock	$ 213	$ (372)
Income (loss) attributable to common stock, shares	380	378
Basic net income (loss) per share (in USD per share)	$ 0.56	$ (0.98)
Effect of Dilutive Securities:
Stock options and other	3
Diluted:
Income (loss) attributable to common stock	$ 213	$ (372)
Income (loss) attributable to common stock, shares	383	378
Diluted net income (loss) per share (in USD per share)	$ 0.56	$ (0.98)