Accumulated Other Comprehensive Income - Components of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 201,380	[1]	$ 197,835
Net unrealized gains (losses) on securities available for sale, net of tax	$ 192	$ (925)	1,421		898
Reclassification adjustment for realized gains on securities, net of tax	0	(48)	(383)		(430)
Ending Balance	210,214	203,713	210,214		203,713
Net unrealized gains (losses) on securities available for sale, tax	104	(499)	765		483
Reclassification adjustment for realized gains on securities, tax	0	(25)	(207)		(231)
Net Unrealized Gains on Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	696	5,563	(150)		4,122
Net unrealized gains (losses) on securities available for sale, net of tax	192	(925)	1,421		898
Reclassification adjustment for realized gains on securities, net of tax	0	(48)	(383)		(430)
Ending Balance	888	4,590	888		4,590
Adjustments Related to Pension Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(1,724)	(1,832)	(1,724)		(1,832)
Net unrealized gains (losses) on securities available for sale, net of tax	0	0	0		0
Reclassification adjustment for realized gains on securities, net of tax	0	0	0		0
Ending Balance	(1,724)	(1,832)	(1,724)		(1,832)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(1,028)	3,731	(1,874)		2,290
Ending Balance	$ (836)	$ 2,758	$ (836)		$ 2,758

[1] Derived from audited consolidated financial statements.