Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income available to common equity	$ 430,199	$ 251,744
Less: Income attributable to unvested stock-based compensation awards	(2,106)	(1,043)
Net income available to common shareholders	$ 428,093	$ 250,701
Adjusted weighted-average shares outstanding:
Common and unvested stock-based compensation awards	129,414	130,440
Less: Unvested stock-based compensation awards	(877)	(744)
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	132	59
Adjusted weighted-average shares outstanding	128,669	129,755
Diluted earnings per common share	$ 3.33	$ 1.93