Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains on available-for-sale securities, net	$ 1,325	$ 524
Interest on deposits	12,781	11,814
Interest on junior subordinated debentures	2,220	1,933
Income before taxes	78,497	63,035
Income tax expense	(29,386)	(23,983)
Net income	49,111	39,052
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 on available-for-sale securities, net	1,325	524
Income before taxes	1,325	524
Income tax expense	(521)	(206)
Net income	804	318
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	255	0
Interest on junior subordinated debentures	468	414
Income before taxes	(723)	(414)
Income tax expense	284	162
Net income	$ (439)	$ (252)