Earnings Per Common Share - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 95,056	$ 111,836	$ 242,881	$ 339,918
Less: Preferred stock dividends	0	2,016	2,016	6,047
Redemption of preferred stock	0	0	5,514	0
Net income available to common shareholders	95,056	109,820	235,351	333,871
Less: Earnings allocated to participating securities	877	876	2,236	2,761
Distributed earnings allocated to common stock	44,546	44,370	133,511	131,069
Undistributed earnings allocated to common stock	49,633	64,574	99,604	200,041
Net earnings allocated to common stock	$ 94,179	$ 108,944	$ 233,115	$ 331,110
Weighted-average shares outstanding for basic earnings per common share	62,726,542	62,566,128	62,655,393	62,786,501
Dilutive effect of stock compensation	193,116	592,866	263,028	725,911
Weighted-average shares outstanding for diluted earnings per common share	62,919,658	63,158,994	62,918,421	63,512,412