Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	$ 544,294	$ 514,279
Nonaccrual	2,811	3,278
Total Loans	551,533	520,980
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	3,308	3,021
Nonaccrual	388	77
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	886	358
Nonaccrual	17	557
90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	234	44
Nonaccrual	1,366	1,544
Residential first mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	211,336	194,830
Nonaccrual	759	1,126
Total Loans	214,905	198,167
Residential first mortgages | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	1,814	1,916
Nonaccrual	388	77
Residential first mortgages | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	816	295
Nonaccrual	0	0
Residential first mortgages | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	180	0
Nonaccrual	300	977
Home equity loans and lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	89,865	90,557
Nonaccrual	451	340
Total Loans	90,736	91,359
Home equity loans and lines of credit | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	353	460
Nonaccrual	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	13	0
Nonaccrual	17	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	54	2
Nonaccrual	434	340
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	178,089	165,318
Nonaccrual	1,001	1,073
Total Loans	179,891	166,994
Commercial real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	790	561
Nonaccrual	0	0
Commercial real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	11	0
Nonaccrual	0	557
Commercial real estate | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	42
Nonaccrual	632	119
Commercial business
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	57,837	56,972
Nonaccrual	600	726
Total Loans	58,797	57,788
Commercial business | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	323	56
Nonaccrual	0	0
Commercial business | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	37	34
Nonaccrual	0	0
Commercial business | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonaccrual	0	95
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Not Past Due	7,167	6,602
Nonaccrual	0	13
Total Loans	7,204	6,672
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	28	28
Nonaccrual	0	0
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	9	29
Nonaccrual	0	0
Consumer | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Accruing Loans Past Due	0	0
Nonaccrual	$ 0	$ 13