Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before taxes	$ 134,601	$ 122,814	$ 363,419	$ 352,471
Income tax expense	(35,480)	(30,866)	(93,686)	(88,962)
Interest on deposits	76,168	48,736	204,168	110,578
Interest on other borrowings	3,466	2,003	10,624	5,400
Interest on junior subordinated debentures	2,897	2,940	9,111	8,239
Net income	99,121	91,948	269,733	263,509
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	400	1,001	856	6
Income before taxes	400	1,001	856	6
Income tax expense	(108)	(271)	(230)	(1)
Net income	292	730	626	5
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	2,428	2,319	10,071	4,338
Income tax expense	(647)	(623)	(2,685)	(1,166)
Interest on deposits	(2,635)	(2,319)	(10,403)	(4,338)
Interest on other borrowings	196	0	321	0
Interest on junior subordinated debentures	11	0	11	0
Net income	$ 1,781	$ 1,696	$ 7,386	$ 3,172