Loans - Analysis of the age of the loan delinquencies by type and by amount past due (Details 2) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,255	$ 852
Current	279,317	263,121
Loans	280,572	263,973
30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,155	699
60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	100	153
Real estate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,210	852
Current	273,907	259,372
Loans	275,117	260,224
Real estate loans | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,155	699
Real estate loans | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	55	153
Real estate loans | Secured by one-to-four family residences
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,205	852
Current	218,636	206,042
Loans	219,841	206,894
Real estate loans | Secured by one-to-four family residences | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,150	699
Real estate loans | Secured by one-to-four family residences | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Secured by one-to-four family residences | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	55	153
Real estate loans | Secured by multi-family residences
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	10,337	10,650
Loans	10,337	10,650
Real estate loans | Secured by multi-family residences | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Secured by multi-family residences | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Secured by multi-family residences | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	6,277	10,750
Loans	6,277	10,750
Real estate loans | Construction | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Construction | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Construction | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	21,650	14,803
Loans	21,650	14,803
Real estate loans | Commercial | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Commercial | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Commercial | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5	0
Current	17,007	17,127
Loans	17,012	17,127
Real estate loans | Home equity lines of credit | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5	0
Real estate loans | Home equity lines of credit | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Real estate loans | Home equity lines of credit | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Other Loans Portfolio Segment | Commercial & industrial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	45	0
Current	5,354	3,679
Loans	5,399	3,679
Other Loans Portfolio Segment | Commercial & industrial loans | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Other Loans Portfolio Segment | Commercial & industrial loans | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Other Loans Portfolio Segment | Commercial & industrial loans | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	45	0
Other Loans Portfolio Segment | Other loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	56	70
Loans	56	70
Other Loans Portfolio Segment | Other loans | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Other Loans Portfolio Segment | Other loans | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Other Loans Portfolio Segment | Other loans | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 0	$ 0