Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Combined Federal And State Income Tax Rate	37.00%	37.00%
CombinedFederalandStateDeferredTaxRate	23.00%
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (7,012)	$ (3,832)
Other comprehensive income before reclassifications	5,186	(964)
Amounts reclassified from other comprehensive loss	(2,819)	(2,216)
Other Comprehensive Income (Loss), Net of Tax	2,367	(3,180)	$ 327
ReclasificationofResidualtTaxImpactofTaxRateChange	0
Ending balance	(5,644)	(7,012)	(3,832)
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(4,660)	(4,759)
Other comprehensive income before reclassifications	528	99
Amounts reclassified from other comprehensive loss	0	0
Other Comprehensive Income (Loss), Net of Tax	528	99
ReclasificationofResidualtTaxImpactofTaxRateChange	(901)
Ending balance	(5,033)	(4,660)	(4,759)
Unrealized Gains (Losses) on Securities Available-for-Sale
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(2,352)	927
Other comprehensive income before reclassifications	4,658	(1,063)
Amounts reclassified from other comprehensive loss	(2,819)	(2,216)
Other Comprehensive Income (Loss), Net of Tax	1,839	(3,279)
ReclasificationofResidualtTaxImpactofTaxRateChange	(98)
Ending balance	(611)	(2,352)	927
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	2,367	$ (3,180)	$ 327
ReclasificationofResidualtTaxImpactofTaxRateChange	$ (999)