Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on deposits	$ 60,976	$ 26,549
Interest on other borrowings	3,633	1,699
Income before taxes	118,645	108,066
Income tax expense	(29,499)	(26,085)
Net income	89,146	81,981
Reclassification Out of Accumulated Other Comprehensive Income | Accumulated Unrealized Losses on Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Gains (losses) on investment securities, net	(67)	(975)
Income before taxes	(67)	(975)
Income tax expense	18	262
Net income	(49)	(713)
Reclassification Out of Accumulated Other Comprehensive Income | Accumulated Unrealized Gains on Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on deposits	(3,589)	(680)
Interest on other borrowings	27	0
Income before taxes	3,562	680
Income tax expense	(950)	(183)
Net income	$ 2,612	$ 497