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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 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	(7)	$ (10)
Amounts reclassified from AOCI, All Other	(851)	3,594
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans	0
Amount reclassified into net income: Net actuarial loss	525	420
Other comprehensive income	80,980	(63,394)
Other comprehensive income, defined pension and post retirement plans	525	420
Ending Balance, March 31, 2019	3,024
Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018	1,888
OCI before reclassifications	81,313
Other comprehensive income	80,462
Ending Balance, March 31, 2019	82,350
Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018	1,888
OCI before reclassifications	81,313
Amounts reclassified from AOCI	(858)
Other comprehensive income	80,455
Ending Balance, March 31, 2019	82,343
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	0
Ending Balance, March 31, 2019	(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	(7)
Ending Balance, March 31, 2019	64
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	525
Ending Balance, March 31, 2019	(79,319)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance, December 31, 2018	(77,956)
OCI before reclassifications	81,313
Amounts reclassified from AOCI	(333)
Other comprehensive income	80,980	$ (63,394)
Ending Balance, March 31, 2019	$ 3,024

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