Earnings Per Common Share - Computations of Basic Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income available to common shareholders:
Net income	$ 447,249	$ 268,822
Less: Preferred stock dividends	(17,050)	(17,078)
Net income available to common equity	430,199	251,744
Less: Income attributable to unvested stock-based compensation awards	(2,108)	(1,043)
Net income available to common shareholders	$ 428,091	$ 250,701
Weighted-average shares outstanding:
Common shares outstanding (including common stock issuable) and unvested stock-based compensation awards	129,414	130,440
Less: Unvested stock-based compensation awards	(877)	(744)
Weighted-average shares outstanding	128,537	129,696
Basic earnings per common share	$ 3.33	$ 1.93