Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains (losses) on investment securities, net	$ 3,305	$ (98)	$ 6,070	$ 402
Interest on deposits	15,621	12,436	41,996	36,246
Interest on junior subordinated debentures	2,400	2,124	6,973	6,034
Income before taxes	85,054	62,197	243,522	195,358
Income tax expense	(31,939)	(23,842)	(91,255)	(74,120)
Net income	53,115	38,355	152,267	121,238
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Unrealized Gains (Losses) on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains (losses) on investment securities, net	3,305	(98)	6,070	402
Income before taxes	3,305	(98)	6,070	402
Income tax expense	(1,300)	38	(2,386)	(158)
Net income	2,005	(60)	3,684	244
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	528	92	1,121	92
Interest on junior subordinated debentures	537	479	1,499	1,350
Income before taxes	(1,065)	(571)	(2,620)	(1,442)
Income tax expense	419	224	1,030	565
Net income	$ (646)	$ (347)	$ (1,590)	$ (877)