Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), before Tax	$ (43,728)		$ 15,926
Deferred tax expense (benefit)	(10,057)		3,663
Accumulated other comprehensive income (loss), net of tax	(33,671)		12,263
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,428	$ 10,419
Unrealized Losses on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), before Tax	36,570		102,278
Deferred tax expense (benefit)	8,411		23,524
Accumulated other comprehensive income (loss), net of tax	28,159		78,754
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	7,089	15,242
Unrealized Losses On Securities Available For Sale Transferred To Held To Maturity
Accumulated Other Comprehensive Income (Loss), before Tax	4,924		5,399
Deferred tax expense (benefit)	1,133		1,242
Accumulated other comprehensive income (loss), net of tax	3,791		4,157
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	366	0
Funded Status of Defined Benefit Plan
Accumulated Other Comprehensive Income (Loss), before Tax	(85,222)		(91,751)
Deferred tax expense (benefit)	(19,601)		(21,103)
Accumulated other comprehensive income (loss), net of tax	(65,621)		$ (70,648)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(5,027)	(4,823)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	$ 6,529	$ 6,264