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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 21,659	$ 81,466	$ 84,471	$ 170,612
Less: Preferred stock dividends	2,050	2,050	4,100	4,100
Net income applicable to common shares	$ 19,609	$ 79,416	$ 80,371	$ 166,512
Weighted average common shares outstanding (in shares)	57,567	56,662	57,593	56,596
Effect of dilutive potential common shares
Common stock equivalents (in shares)	414	699	481	700
Average common shares and dilutive common shares (in shares)	57,981	57,361	58,074	57,296
Net income per common share:
Basic (usd per share)	$ 0.34	$ 1.40	$ 1.40	$ 2.94
Diluted (usd per share)	$ 0.34	$ 1.38	$ 1.38	$ 2.91