Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income available to common shareholders:
Net income	$ 275,344	$ 294,479	$ 788,697	$ 917,058
Less: Preferred stock dividends	(20,443)	(13,363)	(55,560)	(40,088)
Amortization of preferred stock discount		(2,235)		(6,575)
Net income available to common equity	254,901	278,881	733,137	870,395
Less: Income attributable to unvested stock-based compensation awards	(2,996)	(3,545)	(8,830)	(11,451)
Net income available to common shareholders	$ 251,905	$ 275,336	$ 724,307	$ 858,944
Weighted-average shares outstanding:
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	132,832	130,836	132,372	130,088
Less: Unvested stock-based compensation awards	(1,567)	(1,665)	(1,590)	(1,719)
Weighted-average shares outstanding	131,265	129,171	130,782	128,369
Basic earnings per common share	$ 1.92	$ 2.13	$ 5.54	$ 6.69