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				9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Net income from continuing operations	$ 79			$ 110	$ 207	$ 52
Net income (loss) from discontinued operations				8		(322)
Net Income (Loss)	$ 79	$ 53	$ 75	$ 118	$ 207	$ (270)
Average shares outstanding	252			249	251	245
Adjustment to shares outstanding
Weighted Average Shares Outstanding for Computation of Basic Earnings Per Share of Common Stock	252			249	251	245
Net effect of potentially dilutive shares					1
Weighted Average Shares Outstanding for Computation of Diluted Earnings Per Share of Common Stock	252			249	252	245
Basic and Diluted Earnings per Share
Earnings per share of common stock from continuing operations	$ 0.31			$ 0.44	$ 0.82	$ 0.21
Earnings (loss) per share of common stock from discontinued operations				$ 0.04		$ (1.31)
Basic and diluted earnings (loss) per share	$ 0.31			$ 0.48	$ 0.82	$ (1.10)