Other Comprehensive Income (Loss) (Component Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive loss before reclassifications	$ 17,693,000	$ 14,335,000
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(483,000)	(206,000)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	18,176,000	14,541,000
Other comprehensive income (loss)	17,693,000	14,335,000
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax	18,176,000	14,541,000
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(483,000)	(206,000)
Changes in pension plan assets and benefit obligations, Net-of-tax amount	(26,674,000)	(29,672,000)	$ 26,674,000	$ 29,672,000
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(937,000)	(206,000)	(454,000)	0
Unrealized gains on available-for-sale securities, Net-of-tax amount	35,715,000	(5,575,000)	17,539,000	(20,116,000)
Total accumulated other comprehensive income (loss), Net-of-tax amount	8,104,000	(35,453,000)	$ (9,589,000)	$ (49,788,000)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax	$ 0	$ 0