Investment Securities (Schedule Of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,035,743	$ 1,187,499
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	52,548	28,425
Securities Available-for-Sale, Gross Unrealized Holding Losses	70	6,223
Debt Securities, Available-for-sale	1,088,221	1,209,701
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	280,371	302,928
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	23,396	17,563
Debt Securities, Available-for-sale	303,767	320,491
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	755,372	884,571
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	29,152	10,862
Securities Available-for-Sale, Gross Unrealized Holding Losses	70	6,223
Debt Securities, Available-for-sale	$ 784,454	$ 889,210

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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