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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 81,466	$ 89,580	$ 170,612	$ 171,561
Less: Preferred stock dividends	2,050	2,050	4,100	4,100
Net income applicable to common shares	$ 79,416	$ 87,530	$ 166,512	$ 167,461
Weighted average common shares outstanding (in shares)	56,662	56,299	56,596	56,218
Effect of dilutive potential common shares
Common stock equivalents (in shares)	699	928	700	909
Average common shares and dilutive common shares (in shares)	57,361	57,227	57,296	57,127
Net income per common share:
Basic (usd per share)	$ 1.40	$ 1.55	$ 2.94	$ 2.98
Diluted (usd per share)	$ 1.38	$ 1.53	$ 2.91	$ 2.93