Income Taxes - Income tax provision differs from federal income tax rate to pretax income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Computed expected tax expense	$ 3,698	$ 3,585	$ 3,374
Tax-exempt income	(796)	(829)	(959)
Low income housing tax credits	(408)	(120)	(211)
Merger related expenses	267	0	0
Other, net	52	79	137
Total income tax expense	$ 2,813	$ 2,715	$ 2,341