Weighted Average Common Shares - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Restricted stock granted				1,205,569	1,561,300
Performance shares granted				279,093	420,628
Out-of-the-money stock options		3,680,344	11,519,000	4,661,606	8,810,000
Repurchase of outstanding common stock	$ 4,000
Number of shares purchased		6,530,000
Shares purchased value		500		500
Additional amount of common stock that may be repurchased under this board authorized plan		$ 3,500
Performance share units [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Out-of-the-money stock options			412,977		412,977