Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 2,801,500	$ 2,790,248
Available-for-sale securities, unrealized gains	131,850	34,481
Available-for-sale securities, unrealized losses	(792)	(10,047)
Available for sale, at fair value	2,932,558	2,814,682
Held to maturity, at amortized cost	3,034	3,260
Held-to-maturity securities, unrecognized gains	849	1,003
Held-to-maturity securities, unrecognized losses	0	0
Held-to-maturity securities, fair value	3,883	4,263
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	698,243	642,009
Available-for-sale securities, unrealized gains	64,271	5,919
Available-for-sale securities, unrealized losses	(312)	(4,324)
Available for sale, at fair value	762,202	643,604
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	263,546	251,531
Available-for-sale securities, unrealized gains	15,996	9,600
Available-for-sale securities, unrealized losses	(31)	(37)
Available for sale, at fair value	279,511	261,094
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	1,839,711	1,896,708
Available-for-sale securities, unrealized gains	51,583	18,962
Available-for-sale securities, unrealized losses	(449)	(5,686)
Available for sale, at fair value	1,890,845	1,909,984
Held to maturity, at amortized cost	3,034	3,260
Held-to-maturity securities, unrecognized gains	849	1,003
Held-to-maturity securities, unrecognized losses	0	0
Held-to-maturity securities, fair value	$ 3,883	$ 4,263

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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