Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before taxes	$ 30,703	$ 110,173	$ 117,786	$ 228,818
Income tax expense	(9,044)	(28,707)	(33,315)	(58,206)
Interest on deposits	50,057	67,024	117,492	128,000
Interest on junior subordinated debentures	2,752	3,064	5,563	6,214
Net income	21,659	81,466	84,471	170,612
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	(341)	523	150	456
Income before taxes	(341)	523	150	456
Income tax expense	92	(140)	(40)	(122)
Net income	(249)	383	110	334
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	(5,451)	4,081	(6,541)	7,643
Income tax expense	1,453	(1,088)	1,744	(2,038)
Interest on deposits	4,363	(4,179)	4,922	(7,768)
Interest on other borrowings	426	98	718	125
Interest on junior subordinated debentures	662	0	901	0
Net income	$ (3,998)	$ 2,993	$ (4,797)	$ 5,605