Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	$ 514,279	$ 430,512
Nonperforming, Non Accrual	3,278	3,069
Total Loans	520,980	435,096
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	3,021	1,424
Nonperforming, Non Accrual	77	0
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	358	91
Nonperforming, Non Accrual	557	79
90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	44	0
Nonperforming, Non Accrual	1,544	1,588
Residential first mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	194,830	136,924
Nonperforming, Non Accrual	1,126	1,209
Total Loans	198,167	139,305
Residential first mortgages | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	1,916	1,097
Nonperforming, Non Accrual	77	0
Residential first mortgages | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	295	75
Nonperforming, Non Accrual	0	79
Residential first mortgages | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonperforming, Non Accrual	977	1,055
Home equity loans and lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	90,557	86,691
Nonperforming, Non Accrual	340	395
Total Loans	91,359	87,410
Home equity loans and lines of credit | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	460	308
Nonperforming, Non Accrual	0	0
Home equity loans and lines of credit | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	16
Nonperforming, Non Accrual	0	0
Home equity loans and lines of credit | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	2	0
Nonperforming, Non Accrual	340	381
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	165,318	128,945
Nonperforming, Non Accrual	1,073	746
Total Loans	166,994	129,691
Commercial real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	561	0
Nonperforming, Non Accrual	0	0
Commercial real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonperforming, Non Accrual	557	0
Commercial real estate | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	42	0
Nonperforming, Non Accrual	119	123
Commercial business
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	56,972	71,229
Nonperforming, Non Accrual	726	719
Total Loans	57,788	71,948
Commercial business | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	56	0
Nonperforming, Non Accrual	0	0
Commercial business | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	34	0
Nonperforming, Non Accrual	0	0
Commercial business | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonperforming, Non Accrual	95	29
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	6,602	6,723
Nonperforming, Non Accrual	13	0
Total Loans	6,672	6,742
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	28	19
Nonperforming, Non Accrual	0	0
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	29	0
Nonperforming, Non Accrual	0	0
Consumer | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonperforming, Non Accrual	$ 13	$ 0