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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			$ (77,956)
Amounts reclassified from AOCI, Non-credit OTTI			0
Amounts reclassified from AOCI, HTM related	$ (2)	$ (6)	(26)	$ (22)
Amounts reclassified from AOCI, All Other	2,229	8,563	351	14,424
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans			0
Amount reclassified into net income: Net actuarial loss	525	420	1,574	1,260
Other comprehensive income (loss)	29,920	(8,059)	176,382	(87,727)
Other comprehensive income, defined pension and post retirement plans	525	420	1,574	1,260
Ending Balance, September 30, 2019	98,426		98,426
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			1,888
OCI before reclassifications			174,483
Other comprehensive income (loss)			174,834
Ending Balance, September 30, 2019	176,722		176,722
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			1,888
OCI before reclassifications			174,483
Amounts reclassified from AOCI			325
Other comprehensive income (loss)			174,808
Ending Balance, September 30, 2019	176,696		176,696
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			(71)
OCI before reclassifications			0
Other comprehensive income (loss)			0
Ending Balance, September 30, 2019	(71)		(71)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Held-to-maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			71
OCI before reclassifications			0
Other comprehensive income (loss)			(26)
Ending Balance, September 30, 2019	45		45
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			(79,844)
Amount reclassified into net income: Net actuarial loss			1,574
Ending Balance, September 30, 2019	(78,270)		(78,270)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018			(77,956)
OCI before reclassifications			174,483
Amounts reclassified from AOCI			1,899
Other comprehensive income (loss)	29,920	$ (8,059)	176,382	$ (87,727)
Ending Balance, September 30, 2019	$ 98,426		$ 98,426

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