Allowance for Loan Losses and Reserve for Unfunded Lending Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan Losses
Balance, beginning of year	$ 12,801	$ 12,601	$ 12,427
Provision for loan losses	1,016	250	950
Charge-offs	(690)	(326)	(1,200)
Recoveries	476	276	424
Balance, end of year	13,603	12,801	12,601
Reserve for Unfunded Lending Commitments
Balance, beginning of year	203	184	163
Provision for unfunded commitments	3	19	21
Charge-offs	0	0	0
Balance, end of year	$ 206	$ 203	$ 184