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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	$ 220,186
Amounts reclassified from AOCI, HTM related	(2)	$ 20
Amount reclassified into net income: Net actuarial loss	547	596
Other comprehensive loss	(85,586)	(103,867)
Other comprehensive income, defined pension and post retirement plans	547	596
Ending Balance, March 31, 2021	134,600
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	307,790
OCI before reclassifications	(81,613)
Amounts reclassified from AOCI, All Other	477
Other comprehensive loss	(81,136)
Ending Balance, March 31, 2021	226,654
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	305,250
OCI before reclassifications	(90,556)
Amounts reclassified from AOCI	4,423
Other comprehensive loss	(86,133)
Ending Balance, March 31, 2021	219,117
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	(2,546)
OCI before reclassifications	(8,943)
Amounts reclassified from AOCI, Credit loss related	3,948
Other comprehensive loss	(4,995)
Ending Balance, March 31, 2021	(7,541)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Held-to-maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	6
OCI before reclassifications	0
Amounts reclassified from AOCI, HTM related	(2)
Other comprehensive loss	(2)
Ending Balance, March 31, 2021	4
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	(85,064)
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans	0
Amount reclassified into net income: Net actuarial loss	547
Ending Balance, March 31, 2021	(84,517)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2020	220,186
OCI before reclassifications	(90,556)
Amounts reclassified from AOCI	4,970
Other comprehensive loss	(85,586)	$ (103,867)
Ending Balance, March 31, 2021	$ 134,600

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Net of tax amount of the reclassification adjustment related to held-to-maturity securities transferred from the available-for-sale category. This amount includes amortization and amounts realized from the disposal of these securities.

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