Shareholders' Equity And Earnings Per Share (Other Comprehensive Income Reclassified from AOCI) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before taxes	$ 206,859	$ 87,083
Income tax expense	(53,711)	(24,271)
Interest on deposits	27,944	67,435
Interest on junior subordinated debentures	2,704	2,811
Net income	153,148	62,812
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	210	491
Income before taxes	210	491
Income tax expense	(56)	(132)
Net income	154	359
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	(6,696)	(1,090)
Income tax expense	1,784	291
Interest on deposits	4,897	559
Interest on other borrowings	669	292
Interest on junior subordinated debentures	1,130	239
Net income	$ (4,912)	$ (799)