Investment Securities (Schedule Of Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 980,047	$ 1,187,499
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	52,799	28,425
Securities Available-for-Sale, Gross Unrealized Holding Losses	32	6,223
Debt Securities, Available-for-sale	1,032,814	1,209,701
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	279,810	302,928
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	24,696	17,563
Debt Securities, Available-for-sale	304,506	320,491
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	698,237	884,571
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28,092	10,862
Securities Available-for-Sale, Gross Unrealized Holding Losses	32	6,223
Debt Securities, Available-for-sale	726,297	$ 889,210
Corporate Debt Securities
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	11
Debt Securities, Available-for-sale	$ 2,011