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
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 153,148	$ 62,812
Less: Preferred stock dividends	6,991	2,050
Net income applicable to common shares	$ 146,157	$ 60,762
Weighted average common shares outstanding (in shares)	56,904	57,620
Effect of dilutive potential common shares
Common stock equivalents (in shares)	681	575
Average common shares and dilutive common shares (in shares)	57,585	58,195
Net income per common share:
Basic (usd per share)	$ 2.57	$ 1.05
Diluted (usd per share)	$ 2.54	$ 1.04