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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 43,831	$ 38,541	$ 82,883	$ 73,041
Less: Preferred stock dividends and discount accretion	1,580	1,581	3,161	3,162
Net income applicable to common shares—Basic	42,251	36,960	79,722	69,879
Add: Dividends on convertible preferred stock, if dilutive	1,580	1,581	3,161	3,162
Net income applicable to common shares—Diluted	$ 43,831	$ 38,541	$ 82,883	$ 73,041
Weighted average common shares outstanding	47,567	46,520	47,404	46,358
Effect of dilutive potential common shares
Common stock equivalents	1,085	1,327	1,149	1,381
Convertible preferred stock, if dilutive	3,071	3,075	3,071	3,075
Total dilutive potential common shares	4,156	4,402	4,220	4,456
Weighted average common shares and effect of dilutive potential common shares	51,723	50,922	51,624	50,814
Net income per common share-Basic	$ 0.89	$ 0.79	$ 1.68	$ 1.51
Net income per common share-Diluted	$ 0.85	$ 0.76	$ 1.61	$ 1.44