Loans - Analysis of the age of the loan delinquencies by type and by amount past due (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,777	$ 1,071
Current	280,156	282,268
Loans	281,933	283,339
30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,020	622
60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	263	349
90 Days and Over And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	146	100
90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	348	100
Real estate loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,732	1,026
Current	273,132	274,973
Loans	274,864	275,999
Real estate loans | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,020	622
Real estate loans | 60-89 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	263	349
Real estate loans | 90 Days and Over And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	146	0
Real estate loans | 90 Days and Over
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	303	55
Real estate loans | Secured by one-to-four family residences
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,256	631
Current	220,442	220,971
Loans	221,698	221,602
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	938	227
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	263	349
Real estate loans | Secured by one-to-four family residences | 90 Days and Over 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	55
Real estate loans | Secured by multi-family residences
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	9,999	10,241
Loans	9,999	10,241
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 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	4,475	4,898
Loans	4,475	4,898
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 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	248	248
Current	21,771	22,244
Loans	22,019	22,492
Real estate loans | Commercial | 30-59 Days Past Due And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	248
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 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	248	0
Real estate loans | Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	228	147
Current	16,445	16,619
Loans	16,673	16,766
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	82	147
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 And Accruing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	146	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	45
Current	6,982	7,245
Loans	7,027	7,290
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 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	45
Other Loans Portfolio Segment | Other loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Current	42	50
Loans	42	50
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 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