Stock-Based Compensation, Dividend Restrictions, and Calculations of Earnings Per Share of Common Stock - Calculation of Earnings Per Share of Common Stock (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Net Income from Continuing Operations					$ 58	$ 110	$ 53	$ (111)	$ 242	$ 110	$ 218
Net (loss) income from discontinued operations						8	(11)	(319)		(322)	67
Net Income (loss)	$ 35	$ 79	$ 53	$ 75	$ 58	$ 118	$ 42	$ (430)	$ 242	$ (212)	$ 285
Average shares outstanding									251	246	229
Adjustment to shares outstanding									0	0	0
Weighted Average Shares Outstanding for Computation of Basic Earnings Per Share of Common Stock									251	246	229
Net effect of potentially dilutive shares									1		1
Weighted Average Shares Outstanding for Computation of Diluted Earnings Per Share of Common Stock									252	246	230
Basic earnings per share of common stock from continuing operations									$ 0.96	$ 0.45	$ 0.95
Basic (loss) earnings per share of common stock from discontinued operations										$ (1.31)	$ 0.30
Basic earnings (loss) per share									$ 0.96	$ (0.86)	$ 1.25
Diluted earnings per share of common stock from continuing operations									$ 0.96	$ 0.45	$ 0.95
Diluted (loss) earnings per share of common stock from discontinued operations										$ (1.31)	$ 0.29
Diluted earnings (loss) per share									$ 0.96	$ (0.86)	$ 1.24