Fair Value of Financial Instruments - Corporation's assets measured at fair value at the dates indicated on a nonrecurring basis (Details) - USD ($)	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage servicing assets	$ 208,000	$ 382,000	$ 627,000
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-performing loans	8,646,000	4,924,000
Mortgage servicing assets	208,000	382,000
Total assets	8,854,000	5,306,000
Nonrecurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-performing loans	0	0
Mortgage servicing assets	0	0
Total assets	0	0
Nonrecurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-performing loans	899,000	2,042,000
Mortgage servicing assets	0
Total assets	899,000	2,042,000
Nonrecurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-performing loans	7,747,000	2,882,000
Mortgage servicing assets	208,000	382,000
Total assets	$ 7,955,000	$ 3,264,000