Shareholders' Equity And Earnings Per Share (Computation Of Basic And Diluted Earnings Per Common Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Equity [Abstract]
Net income	$ 109,137	$ 107,315	$ 367,394	$ 191,786
Less: Preferred stock dividends	6,991	10,286	20,973	14,386
Net income applicable to common shares	$ 102,146	$ 97,029	$ 346,421	$ 177,400
Weighted average common shares outstanding (in shares)	57,000	57,597	56,985	57,595
Dilutive potential common shares (in shares)	753	449	728	469
Weighted average common shares and effect of dilutive potential common shares (in shares)	57,753	58,046	57,713	58,064
Net income per common share:
Basic (usd per share)	$ 1.79	$ 1.68	$ 6.08	$ 3.08
Diluted (usd per share)	$ 1.77	$ 1.67	$ 6.00	$ 3.06