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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 64,897	$ 50,041	$ 123,275	$ 99,152
Less: Preferred stock dividends	2,050	3,628	5,678	7,256
Net income applicable to common shares	62,847	46,413	117,597	91,896
Add: Dividends on convertible preferred stock, if dilutive	0	1,578	1,578	3,156
Net income applicable to common shares—Diluted	$ 62,847	$ 47,991	$ 119,175	$ 95,052
Weighted average common shares outstanding	54,775	49,140	53,528	48,794
Effect of dilutive potential common shares
Common stock equivalents	927	856	994	778
Convertible preferred stock, if dilutive	885	3,109	1,987	3,109
Total dilutive potential common shares	1,812	3,965	2,981	3,887
Weighted average common shares and effect of dilutive potential common shares	56,587	53,105	56,509	52,681
Net income per common share-Basic (usd per share)	$ 1.15	$ 0.94	$ 2.20	$ 1.88
Net income per common share-Diluted (usd per share)	$ 1.11	$ 0.90	$ 2.11	$ 1.80