Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before taxes	$ 87,083	$ 118,645
Income tax expense	(24,271)	(29,499)
Interest on deposits	67,435	60,976
Interest on junior subordinated debentures	2,811	3,150
Net income	62,812	89,146
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	491	(67)
Income before taxes	491	(67)
Income tax expense	(132)	18
Net income	359	(49)
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]
Income before taxes	(1,090)	3,562
Income tax expense	291	(950)
Interest on deposits	559	(3,589)
Interest on other borrowings	292	27
Interest on junior subordinated debentures	239	0
Net income	$ (799)	$ 2,612