Loans - Credit quality indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 30, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 501,909	$ 517,467
Residential real estate | 1-4 Family
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	325,728	345,915
Residential real estate | 1-4 Family | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	321,960	343,562
Residential real estate | 1-4 Family | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,768	2,353
Residential real estate | Home equity and HELOCs
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	45,093	47,054
Residential real estate | Home equity and HELOCs | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	44,644	46,580
Residential real estate | Home equity and HELOCs | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	449	474
Residential real estate | Construction Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	13,581	15,799
Residential real estate | Construction Residential | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	13,581	15,799
Commercial real estate | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	12,223	14,964
Commercial real estate | Multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	12,040	13,976
Commercial real estate | Multi-family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans		803
Commercial real estate | Multi-family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	183	185
Commercial real estate | Commercial non-residential
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	89,952	76,707
Commercial real estate | Commercial non-residential | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	88,749	75,973
Commercial real estate | Commercial non-residential | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	461	507
Commercial real estate | Commercial non-residential | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	742	227
Commercial real estate | Construction and Land
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	5,818	6,690
Commercial real estate | Construction and Land | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	5,818	6,690
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	6,027	6,438
Commercial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	6,027	6,438
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,487	3,900
Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	3,357	3,785
Consumer | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans	$ 130	$ 115