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, 2020	Mar. 31, 2019
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 62,812	$ 89,146
Less: Preferred stock dividends	2,050	2,050
Net income applicable to common shares	$ 60,762	$ 87,096
Weighted average common shares outstanding (in shares)	57,620	56,529
Effect of dilutive potential common shares
Common stock equivalents (in shares)	575	699
Average common shares and dilutive common shares (in shares)	58,195	57,228
Net income per common share:
Basic (usd per share)	$ 1.05	$ 1.54
Diluted (usd per share)	$ 1.04	$ 1.52