Investment Securities (Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	$ 2,758,147	$ 2,790,248
Available-for-sale securities, unrealized gains	132,650	34,481
Available-for-sale securities, unrealized losses	(322)	(10,047)
Available for sale, at fair value	2,890,475	2,814,682
Investment securities held to maturity	3,200	3,260
Held-to-maturity securities, unrealized gains	865	1,003
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	4,065	4,263
U.S. Treasury and agencies
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	691,066	642,009
Available-for-sale securities, unrealized gains	59,446	5,919
Available-for-sale securities, unrealized losses	0	(4,324)
Available for sale, at fair value	750,512	643,604
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	242,262	251,531
Available-for-sale securities, unrealized gains	10,172	9,600
Available-for-sale securities, unrealized losses	(15)	(37)
Available for sale, at fair value	252,419	261,094
Residential mortgage-backed securities and collateralized mortgage obligations
Investment Holdings [Line Items]
Available-for-sale securities, amortized cost	1,824,819	1,896,708
Available-for-sale securities, unrealized gains	63,032	18,962
Available-for-sale securities, unrealized losses	(307)	(5,686)
Available for sale, at fair value	1,887,544	1,909,984
Investment securities held to maturity	3,200	3,260
Held-to-maturity securities, unrealized gains	865	1,003
Held-to-maturity securities, unrealized losses	0	0
Held-to-maturity securities, fair value	$ 4,065	$ 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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Amortized cost 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 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 of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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