Income Taxes - Significant Components of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Allowance for loan losses	$ 13,463	$ 12,440
Net unrealized holding losses on securities available-for-sale	1,091	0
Other employee benefits	2,712	3,095
Low income housing partnerships	3,249	3,213
Net adjustment to funded status of pension	5,173	6,481
Impairment of securities	8	300
State net operating loss carryforwards	4,573	3,598
Other	2,848	2,355
Gross Deferred Tax Assets	33,117	31,482
Less: Valuation allowance	(4,573)	(3,598)
Total Deferred Tax Assets	28,544	27,884
Deferred Tax Liabilities Unrealized Gains Losses For Available For Sale Securities	0	638
Deferred Tax Liabilities:
Prepaid pension	(6,164)	(1,749)
Deferred loan income	(3,219)	(2,937)
Purchase accounting adjustments	(100)	(100)
Depreciation on premises and equipment	(477)	(480)
Other	(1,375)	(1,401)
Total Deferred Tax liabilities	(11,335)	(7,305)
Net Deferred Tax Asset	$ 17,209	$ 20,579