Equity and Earnings Per Share - Calculations of Earnings Per Share of Common Stock (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Net income (loss) from continuing operations	$ 53		$ 53	$ 128	$ (58)
Net loss from discontinued operations	0		(11)	0	(330)
Net Income (Loss)	$ 53	$ 75	$ 42	$ 128	$ (388)
Average shares outstanding	251		249	251	243
Adjustment to shares outstanding	0			0
Weighted Average Shares Outstanding for Computation of Basic Earnings Per Share of Common Stock	251		249	251	243
Net effect of potentially dilutive shares	1			0
Weighted Average Shares Outstanding for Computation of Diluted Earnings Per Share of Common Stock	252		249	251	243
Basic and Diluted Earnings per Share
Earnings (loss) per share of common stock from continuing operations	$ 0.21		$ 0.21	$ 0.51	$ (0.24)
Loss per share of common stock from discontinued operations	$ 0.00		$ (0.04)	$ 0.00	$ (1.36)
Basic and diluted earnings (loss) per share	$ 0.21		$ 0.17	$ 0.51	$ (1.60)