Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income available to common equity	$ 278,881	$ 278,066	$ 870,395	$ 687,296
Less: Income attributable to unvested stock-based compensation awards	(3,525)	(4,170)	(11,395)	(10,454)
Net income available to common shareholders	$ 275,356	$ 273,896	$ 859,000	$ 676,842
Adjusted weighted-average shares outstanding:
Common and unvested stock-based compensation awards	130,836	127,741	130,088	127,449
Less: Unvested stock-based compensation awards	(1,665)	(1,923)	(1,719)	(1,939)
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	1,094	474	943	426
Adjusted weighted-average shares outstanding	130,265	126,292	129,312	125,936
Diluted earnings per common share	$ 2.11	$ 2.17	$ 6.64	$ 5.37