Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before taxes	$ 110,173	$ 121,591	$ 228,818	$ 229,657
Income tax expense	(28,707)	(32,011)	(58,206)	(58,096)
Interest on deposits	67,024	35,293	128,000	61,842
Interest on other borrowings	3,525	1,698	7,158	3,397
Net income	81,466	89,580	170,612	171,561
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	523	(20)	456	(995)
Income before taxes	523	(20)	456	(995)
Income tax expense	(140)	8	(122)	270
Net income	383	(12)	334	(725)
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	4,081	1,339	7,643	2,019
Income tax expense	(1,088)	(360)	(2,038)	(543)
Interest on deposits	(4,179)	(1,339)	(7,768)	(2,019)
Interest on other borrowings	98	0	125	0
Net income	$ 2,993	$ 979	$ 5,605	$ 1,476