Investment Securities (Schedule Of Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,139,189	$ 1,187,499
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45,416	28,425
Securities Available-for-Sale, Gross Unrealized Holding Losses	206	6,223
Debt Securities, Available-for-sale	1,184,399	1,209,701
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	302,329	302,928
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	18,516	17,563
Securities Available-for-Sale, Gross Unrealized Holding Losses	79
Debt Securities, Available-for-sale	320,766	320,491
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	836,860	884,571
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	26,900	10,862
Securities Available-for-Sale, Gross Unrealized Holding Losses	127	6,223
Debt Securities, Available-for-sale	$ 863,633	$ 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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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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