Stockholders' Equity - Reconciliation between Basic and Diluted EPS Table (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Net income (loss)
Net income (loss) attributable to common stockholders	$ 801		$ 2,391		$ (2,649)
Less distributions on participating securities	2		1		0
Less undistributed income allocated to participating securities	4		14		0
Basic	795		2,376		(2,649)
Diluted	$ 795		$ 2,376		$ (2,649)
Shares
Average number of common shares outstanding—basic	502		500		498
Dilutive effect of stock options	3		2		0
Average number of common shares outstanding—diluted	505		502		498
Excluded (1)	4	[1]	6	[1]	12	[1]
Net income (loss) per common share
Basic	$ 1.58		$ 4.76		$ (5.32)
Diluted	$ 1.58		$ 4.74		$ (5.32)
Dividends per common share	$ 0.54		$ 0.36		$ 0.36

[1] Inclusion of certain shares would have had an anti-dilutive effect.