Income Taxes - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts
Income tax computed at federal statutory rates	$ 6,288	$ 6,272	$ 6,084
Tax effect of exclusion of interest income on obligations of states and political subdivisions (in Dollars)	(1,125)	(1,310)	(1,456)
Reduction of interest expense incurred to carry tax-exempt assets	32	36	38
Increase in bank-owned life insurance	(151)	(324)	(159)
State income taxes, net of federal tax benefit	348	403	563
Amortization of investments in qualified affordable housing projects, net of federal tax benefit	255	217	264
Tax credit on investments in qualified affordable housing projects	(390)	(364)	(400)
Share-based compensation	(597)	(476)
Reduction in net deferred tax asset due to change in federal statutory rate	6,643
Other	91	5	(81)
Income tax expense (benefit)	$ 11,394	$ 4,459	$ 4,853
Percent of Pre-tax Income
Income tax computed at federal statutory rates (as a percent)	35.00%	35.00%	35.00%
Tax effect of exclusion of interest income on obligations of states and political subdivisions (as a percent)	(6.30%)	(7.30%)	(8.40%)
Reduction of interest expense incurred to carry tax-exempt assets (as a percent)	0.20%	0.20%	0.20%
Increase in bank-owned life insurance	(0.80%)	(1.80%)	(0.90%)
State income taxes, net of federal tax benefit	1.90%	2.20%	3.30%
Amortization of investments in qualified affordable housing projects	1.40%	1.20%	1.50%
Tax credit on investments in qualified affordable housing projects	(2.20%)	(2.00%)	(2.30%)
Share-based compensation	(3.30%)	(2.70%)
Reduction in net deferred tax asset due to change in federal statutory rate	37.00%
Other	0.50%		(0.50%)
Income tax expense (as a percent)	63.40%	24.80%	27.90%