Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 3,685,650	$ 2,801,500
Available-for-sale securities, unrealized gains	76,427	131,850
Available-for-sale securities, unrealized losses	(38,906)	(792)
Available for sale, at fair value	3,723,171	2,932,558
Investment securities held to maturity	2,795	3,034
Held-to-maturity securities, unrealized gains	786	849
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	3,581	3,883
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	806,469	698,243
Available-for-sale securities, unrealized gains	35,304	64,271
Available-for-sale securities, unrealized losses	(2,796)	(312)
Available for sale, at fair value	838,977	762,202
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	272,275	263,546
Available-for-sale securities, unrealized gains	11,851	15,996
Available-for-sale securities, unrealized losses	(717)	(31)
Available for sale, at fair value	283,409	279,511
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	2,606,906	1,839,711
Available-for-sale securities, unrealized gains	29,272	51,583
Available-for-sale securities, unrealized losses	(35,393)	(449)
Available for sale, at fair value	2,600,785	1,890,845
Investment securities held to maturity	2,795	3,034
Held-to-maturity securities, unrealized gains	786	849
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 3,581	$ 3,883

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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