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
	Mar. 31, 2014	Mar. 31, 2013
Income available to common shareholders:
Net income	$ 229,017	$ 274,113
Less: Preferred stock dividends	(14,674)	(13,363)
Amortization of preferred stock discount		(2,147)
Net income available to common equity	214,343	258,603
Less: Income attributable to unvested stock-based compensation awards	(2,623)	(3,524)
Net income available to common shareholders	$ 211,720	$ 255,079
Weighted-average shares outstanding:
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	131,800	129,449
Less: Unvested stock-based compensation awards	(1,588)	(1,780)
Weighted-average shares outstanding	130,212	127,669
Basic earnings per common share	$ 1.63	$ 2.00