Earnings Per Common Share (Earnings Per Share Basic And Diluted) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share Reconciliation [Abstract]
Net income	$ 60,044	$ 69,281	$ 53,097	$ 38,199	$ 90,473	$ 93,865	$ 98,649	$ 99,736	$ 220,621	$ 382,723	$ 360,418
Less: Preferred stock dividends									7,875	7,875	7,853
Net income available to common shareholders, basic										374,848	352,565
Net income available to common shareholders, diluted									212,746	374,848	352,565
Less: Earnings applicable to participating securities, basic									1,272	1,863	862
Less: Earnings applicable to participating securities, diluted									1,272	1,863	862
Earnings applicable to common shareholders									211,474	372,985	351,703
Earnings applicable to common shareholders, diluted									$ 211,474	$ 372,985	$ 351,703
Earnings per common share:
Earnings per common share, Basic (in dollars per share)	$ 0.64	$ 0.75	$ 0.57	$ 0.40	$ 0.96	$ 1.00	$ 1.05	$ 1.06	$ 2.35	$ 4.07	$ 3.83
Earnings per common share, Diluted (in dollars per share)	$ 0.64	$ 0.75	$ 0.57	$ 0.39	$ 0.96	$ 1.00	$ 1.05	$ 1.06	$ 2.35	$ 4.06	$ 3.81
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted-average common shares outstanding - basic									89,967	91,559	91,930
Stock options and restricted stock (in shares)									184	323	297
Weighted Average Number of Shares Outstanding, Diluted									90,151	91,882	92,227