Loans - Risk category of loans by class (Details 1) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 243,147	$ 227,069
Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	240,842	225,229
Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,305	1,840
Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	240,556	225,047
Real estate loans: | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	238,319	223,254
Real estate loans: | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,237	1,793
Real estate loans: | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Secured by one-to-four family residences
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	196,680	188,573
Real estate loans: | Secured by one-to-four family residences | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	194,685	187,079
Real estate loans: | Secured by one-to-four family residences | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Secured by one-to-four family residences | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,995	1,494
Real estate loans: | Secured by one-to-four family residences | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Secured by multi-family residences
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,217	5,103
Real estate loans: | Secured by multi-family residences | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,217	5,103
Real estate loans: | Secured by multi-family residences | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Secured by multi-family residences | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Secured by multi-family residences | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,807	6,134
Real estate loans: | Construction | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,807	6,134
Real estate loans: | Construction | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Construction | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Construction | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	10,608	8,440
Real estate loans: | Commercial real estate | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	10,608	8,440
Real estate loans: | Commercial real estate | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Commercial real estate | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Commercial real estate | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Home equity lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	17,244	16,797
Real estate loans: | Home equity lines of credit | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	17,002	16,498
Real estate loans: | Home equity lines of credit | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Real estate loans: | Home equity lines of credit | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	242	299
Real estate loans: | Home equity lines of credit | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Other Loans Portfolio Segment | Commercial & industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,518	1,947
Other Loans Portfolio Segment | Commercial & industrial loans | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	2,450	1,900
Other Loans Portfolio Segment | Commercial & industrial loans | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Other Loans Portfolio Segment | Commercial & industrial loans | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	68	47
Other Loans Portfolio Segment | Commercial & industrial loans | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Other Loans Portfolio Segment | Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	73	75
Other Loans Portfolio Segment | Other loans | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	73	75
Other Loans Portfolio Segment | Other loans | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Other Loans Portfolio Segment | Other loans | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Other Loans Portfolio Segment | Other loans | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans