Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains (losses) on available-for-sale securities, net	$ 1,440	$ (24)	$ 2,765	$ 500
Interest on deposits	13,594	11,996	26,375	23,810
Interest on junior subordinated debentures	2,353	1,977	4,573	3,910
Income before taxes	79,971	70,126	158,468	133,161
Income tax expense	(29,930)	(26,295)	(59,316)	(50,278)
Net income	50,041	43,831	99,152	82,883
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Unrealized Losses on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains (losses) on available-for-sale securities, net	1,440	(24)	2,765	500
Income before taxes	1,440	(24)	2,765	500
Income tax expense	(565)	10	(1,086)	(196)
Net income	875	(14)	1,679	304
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Unrealized Losses on Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on deposits	338	0	593	0
Interest on junior subordinated debentures	494	457	962	871
Income before taxes	(832)	(457)	(1,555)	(871)
Income tax expense	327	179	611	341
Net income	$ (505)	$ (278)	$ (944)	$ (530)