Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), before Tax	$ (28,727)		$ (28,727)		$ 15,926
Deferred tax expense (benefit)	(6,607)		(6,607)		3,663
Accumulated other comprehensive income (loss), net of tax	(22,120)		(22,120)		12,263
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	7,389	$ 5,663	9,817	$ 16,082
Unrealized Losses on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), before Tax	45,338		45,338		102,278
Deferred tax expense (benefit)	10,428		10,428		23,524
Accumulated other comprehensive income (loss), net of tax	34,910		34,910		78,754
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	12,189	10,589	19,278	25,831
Unrealized Losses On Securities Available For Sale Transferred To Held To Maturity
Accumulated Other Comprehensive Income (Loss), before Tax	4,139		4,139		5,399
Deferred tax expense (benefit)	952		952		1,242
Accumulated other comprehensive income (loss), net of tax	3,187		3,187		4,157
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	604	0	970	0
Funded Status of Defined Benefit Plan
Accumulated Other Comprehensive Income (Loss), before Tax	(78,204)		(78,204)		(91,751)
Deferred tax expense (benefit)	(17,987)		(17,987)		(21,103)
Accumulated other comprehensive income (loss), net of tax	(60,217)		(60,217)		$ (70,648)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(5,404)	(4,926)	(10,431)	(9,749)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	$ 7,018	$ 6,398	$ 13,547	$ 12,662