Earnings Per Common Share (Basic and Diluted Earnings Per Common Share) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 331,151	$ 443,599	$ 454,918
Less: Preferred stock dividends	2,016	8,063	8,063
Redemption of preferred stock	5,514	0	0
Net income available to common shareholders	323,621	435,536	446,855
Less: Earnings allocated to participating securities	3,136	3,687	3,169
Distributed earnings allocated to common stock	178,863	175,540	164,268
Undistributed earnings allocated to common stock	141,622	256,309	279,418
Net earnings allocated to common stock	$ 320,485	$ 431,849	$ 443,686
Weighted-average shares outstanding for basic earnings per common share	62,727,053	62,741,769	63,704,508
Dilutive effect of stock compensation	276,784	700,101	982,208
Weighted-average shares outstanding for diluted earnings per common share	63,003,837	63,441,870	64,686,716