Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income available to common shareholders:
Net income	$ 495,460	$ 372,136	$ 1,400,778	$ 882,012
Less: Preferred stock dividends	(17,050)	(17,050)	(51,150)	(51,178)
Net income available to common equity	478,410	355,086	1,349,628	830,834
Less: Income attributable to unvested stock-based compensation awards	(2,452)	(1,687)	(6,823)	(3,631)
Net income available to common shareholders	$ 475,958	$ 353,399	$ 1,342,805	$ 827,203
Weighted-average shares outstanding:
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	129,580	129,061	129,529	129,518
Less: Unvested stock-based compensation awards	(891)	(776)	(897)	(768)
Weighted-average shares outstanding	128,689	128,285	128,632	128,750
Basic earnings per common share	$ 3.70	$ 2.75	$ 10.44	$ 6.42