Loans and Allowance for Loan Losses (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Analysis of changes in the allowance for loan losses
Balance at beginning of period	$ 4,868	$ 5,194	$ 5,202
Loan charge-offs	(840)	(614)	(723)
Recoveries	450	238	260
Net loan recoveries (charge-offs)	(390)	(376)	(463)
Provision charged to operations	100	50	455
Balance at end of period	4,578	4,868	5,194
Commercial
Analysis of changes in the allowance for loan losses
Balance at beginning of period	1,394	1,977	2,064
Loan charge-offs			(470)
Recoveries	388	117	134
Net loan recoveries (charge-offs)	388	117	(336)
Provision charged to operations	(191)	(700)	249
Balance at end of period	1,591	1,394	1,977
Commercial real estate
Analysis of changes in the allowance for loan losses
Balance at beginning of period	3,072	2,926	2,754
Loan charge-offs	(654)	(287)	(84)
Recoveries		35	10
Net loan recoveries (charge-offs)	(654)	(252)	(74)
Provision charged to operations	284	398	246
Balance at end of period	2,702	3,072	2,926
Residential real estate
Analysis of changes in the allowance for loan losses
Balance at beginning of period	163	153	229
Loan charge-offs	(14)	(35)	(45)
Recoveries	5	2	37
Net loan recoveries (charge-offs)	(9)	(33)	(8)
Provision charged to operations	(37)	43	(68)
Balance at end of period	117	163	153
Consumer | Home equity
Analysis of changes in the allowance for loan losses
Balance at beginning of period	150	52	60
Loan charge-offs	(26)	(144)
Recoveries	10	23	17
Net loan recoveries (charge-offs)	(16)	(121)	17
Provision charged to operations	(64)	219	(25)
Balance at end of period	70	150	52
Consumer | Other
Analysis of changes in the allowance for loan losses
Balance at beginning of period	89	86	95
Loan charge-offs	(146)	(148)	(124)
Recoveries	47	61	62
Net loan recoveries (charge-offs)	(99)	(87)	(62)
Provision charged to operations	108	90	53
Balance at end of period	$ 98	$ 89	$ 86