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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 107,315	$ 99,121	$ 191,786	$ 269,733
Less: Preferred stock dividends	10,286	2,050	14,386	6,150
Net income applicable to common shares	$ 97,029	$ 97,071	$ 177,400	$ 263,583
Weighted average common shares outstanding (in shares)	57,597	56,690	57,595	56,627
Effect of dilutive potential common shares
Common stock equivalents (in shares)	449	773	469	724
Average common shares and dilutive common shares (in shares)	58,046	57,463	58,064	57,351
Net income per common share:
Basic (usd per share)	$ 1.68	$ 1.71	$ 3.08	$ 4.65
Diluted (usd per share)	$ 1.67	$ 1.69	$ 3.06	$ 4.60