Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 3,278	$ 3,069
Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,100	1,402
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	77	0
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	557	79
90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,544	1,588
Residential first mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,126	1,209
Residential first mortgages | Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	72	75
Residential first mortgages | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	77	0
Residential first mortgages | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	79
Residential first mortgages | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	977	1,055
Home equity loans and lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	340	395
Home equity loans and lines of credit | Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	14
Home equity loans and lines of credit | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Home equity loans and lines of credit | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Home equity loans and lines of credit | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	340	381
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,073	746
Commercial real estate | Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	397	623
Commercial real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Commercial real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	557	0
Commercial real estate | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	119	123
Commercial business
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	726	719
Commercial business | Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	631	690
Commercial business | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Commercial business | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Commercial business | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	95	29
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	13	0
Consumer | Not Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	0	0
Consumer | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 13	$ 0