Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Long-term stock awards, including restoration options	1,000,000	1,000,000
Total unrecognized compensation expense	$ 12	$ 24
Weighted average remaining vesting period in years	2 years	3 years
Total market value (at the vesting date) of stock award shares	32	23
Stock awards granted subsequent to January 1, 2010 have a vesting period, in years	4 years	5 years
Expiration date	6 years	6 years
Grant date exercise price per share	$ 20	$ 12
Stock option shares forfeited	1,000,000	3,000,000
Unvested Awards [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Total unrecognized compensation expense	$ 83	$ 92
Weighted average remaining vesting period in years	4 years	4 years
Stock Option [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Stock awards granted subsequent to January 1, 2010 have a vesting period, in years	5 years	5 years
Stock option shares granted	869,000
Grant date exercise price per share	$ 20
Stock option shares forfeited	1,182,470
Long-Term Stock Awards [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Long-term stock awards, including restoration options	1,623,080
Maximum [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Expiration date	10 years	10 years