Derivative Financial Instruments (Rollforward Of Amounts In Accumulated Other Comprehensive Income Related To Interest Rate Swaps Designated As Cash Flow Hedges) (Detail) - Interest rate contract - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Rollforward of AOCI from Cash Flow Hedging Derivatives [Roll Forward]
Unrealized gain (loss) at beginning of period	$ 10,471	$ (59,503)
Amount reclassified from accumulated other comprehensive income to interest expense on deposits, other borrowings and junior subordinated debentures	6,780	5,667
Amount of income (loss) recognized in other comprehensive income	2,224	4,726
Unrealized gain (loss) at end of period	19,475	(49,110)	$ 19,475	$ (49,110)
Designated as hedging instrument
Rollforward of AOCI from Cash Flow Hedging Derivatives [Roll Forward]
Unrealized gain (loss) at beginning of period			(31,533)	(17,943)
Amount reclassified from accumulated other comprehensive income to interest expense on deposits, other borrowings and junior subordinated debentures			20,342	12,208
Amount of income (loss) recognized in other comprehensive income			30,666	(43,375)
Unrealized gain (loss) at end of period	$ 19,475	$ (49,110)	$ 19,475	$ (49,110)