Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income available to common equity	$ 441,019	$ 224,004	$ 871,218	$ 475,748
Less: Income attributable to unvested stock-based compensation awards	(2,260)	(905)	(4,366)	(1,953)
Net income available to common shareholders	$ 438,759	$ 223,099	$ 866,852	$ 473,795
Adjusted weighted-average shares outstanding:
Common and unvested stock-based compensation awards	129,589	129,059	129,502	129,750
Less: Unvested stock-based compensation awards	(918)	(784)	(898)	(764)
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	171	58	152	58
Adjusted weighted-average shares outstanding	128,842	128,333	128,756	129,044
Diluted earnings per common share	$ 3.41	$ 1.74	$ 6.73	$ 3.67