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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 50,041	$ 43,831	$ 99,152	$ 82,883
Less: Preferred stock dividends and discount accretion	3,628	1,580	7,256	3,161
Net income applicable to common shares	46,413	42,251	91,896	79,722
Add: Dividends on convertible preferred stock, if dilutive	1,578	1,580	3,156	3,161
Net income applicable to common shares—Diluted	$ 47,991	$ 43,831	$ 95,052	$ 82,883
Weighted average common shares outstanding	49,140	47,567	48,794	47,404
Effect of dilutive potential common shares
Common stock equivalents	856	1,085	778	1,149
Convertible preferred stock, if dilutive	3,109	3,071	3,109	3,071
Total dilutive potential common shares	3,965	4,156	3,887	4,220
Weighted average common shares and effect of dilutive potential common shares	53,105	51,723	52,681	51,624
Net income per common share-Basic (usd per share)	$ 0.94	$ 0.89	$ 1.88	$ 1.68
Net income per common share-Diluted (usd per share)	$ 0.90	$ 0.85	$ 1.80	$ 1.61