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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			$ 81,750
Amounts reclassified from AOCI, HTM related	$ (25)	$ (17)	(5)	$ (24)
Amount reclassified into net income: Net actuarial loss	595	524	1,191	1,049
Other comprehensive income	174,083	65,482	70,216	146,462
Other comprehensive income, defined pension and post retirement plans	595	524	1,191	1,049
Ending Balance, June 30, 2020	151,966		151,966
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			170,439
OCI before reclassifications			74,882
Amounts reclassified from AOCI, All Other			7,616
Other comprehensive income			82,498
Ending Balance, June 30, 2020	252,937		252,937
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			170,393
OCI before reclassifications			52,832
Amounts reclassified from AOCI			16,193
Other comprehensive income			69,025
Ending Balance, June 30, 2020	239,418		239,418
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			(71)
OCI before reclassifications			(22,050)
Amounts reclassified from AOCI, OTTI			8,582
Other comprehensive income			(13,468)
Ending Balance, June 30, 2020	(13,539)		(13,539)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Held-to-maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			25
OCI before reclassifications			0
Amounts reclassified from AOCI, HTM related			(5)
Other comprehensive income			(5)
Ending Balance, June 30, 2020	20		20
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			(88,643)
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans			0
Amount reclassified into net income: Net actuarial loss			1,191
Ending Balance, June 30, 2020	(87,452)		(87,452)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2019			81,750
OCI before reclassifications			52,832
Amounts reclassified from AOCI			17,384
Other comprehensive income	174,083	$ 65,482	70,216	$ 146,462
Ending Balance, June 30, 2020	$ 151,966		$ 151,966

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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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