Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), before Tax	$ (41,736)		$ (41,736)		$ 15,926
Deferred tax expense (benefit)	(9,599)		(9,599)		3,663
Accumulated other comprehensive income (loss), net of tax	(32,137)		(32,137)		12,263
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,340	$ 11,622	11,157	$ 27,704
Unrealized Losses on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), before Tax	25,986		25,986		102,278
Deferred tax expense (benefit)	5,977		5,977		23,524
Accumulated other comprehensive income (loss), net of tax	20,009		20,009		78,754
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	6,224	16,497	25,502	42,328
Unrealized Losses On Securities Available For Sale Transferred To Held To Maturity
Accumulated Other Comprehensive Income (Loss), before Tax	3,709		3,709		5,399
Deferred tax expense (benefit)	853		853		1,242
Accumulated other comprehensive income (loss), net of tax	2,856		2,856		4,157
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	331	0	1,301	0
Funded Status of Defined Benefit Plan
Accumulated Other Comprehensive Income (Loss), before Tax	(71,431)		(71,431)		(91,751)
Deferred tax expense (benefit)	(16,429)		(16,429)		(21,103)
Accumulated other comprehensive income (loss), net of tax	(55,002)		(55,002)		$ (70,648)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(5,215)	(4,875)	(15,646)	(14,624)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	$ 6,773	$ 6,332	$ 20,320	$ 18,994