Other Comprehensive Income (Loss) (Component Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	$ 0	$ 0	$ 0	$ 0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	117,000	111,000	355,000	(357,000)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax	(4,997,000)	207,000	(13,736,000)	26,742,000
Other comprehensive loss before reclassifications	(4,880,000)	318,000	(13,381,000)	26,385,000
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	117,000	111,000	355,000	(357,000)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	(4,997,000)	228,000	(13,736,000)	24,146,000
Other comprehensive income (loss)	(4,880,000)	339,000	(13,381,000)	23,789,000
Changes in pension plan assets and benefit obligations, Net-of-tax amount	(34,421,000)	(26,674,000)	(34,421,000)	(26,674,000)	$ 34,421,000	$ 34,421,000	$ 26,674,000	$ 26,674,000
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(343,000)	(811,000)	(343,000)	(811,000)	(460,000)	(698,000)	(922,000)	(454,000)
Unrealized gains on available-for-sale securities, Net-of-tax amount	26,954,000	41,685,000	26,954,000	41,685,000	31,951,000	40,690,000	41,457,000	17,539,000
Total accumulated other comprehensive income (loss), Net-of-tax amount	(7,810,000)	14,200,000	(7,810,000)	14,200,000	$ (2,930,000)	$ 5,571,000	$ 13,861,000	$ (9,589,000)
Debt Securities, Realized Gain (Loss)	0	27,000	0	(3,286,000)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	$ 0	$ 21,000	$ 0	$ (2,596,000)