Fair Value Measurements - Schedule of financial instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Jun. 30, 2020
Letter of Credit
Carrying amount of financial instruments	$ 0	$ 0
Line of Credit
Carrying amount of financial instruments	0	0
Financial liabilities | Subordinated Debt
Carrying amount of financial instruments	15,218	15,142
Financial liabilities | Federal Home Loan Bank Advances
Carrying amount of financial instruments	62,781	70,024
Financial assets | Loans Receivable
Carrying amount of financial instruments	2,134,885	2,141,929
Financial assets | Cash and Cash Equivalents
Carrying amount of financial instruments	236,896	54,245
Financial assets | Interest-bearing time deposits
Carrying amount of financial instruments	977	974
Financial assets | Investment in Federal Home Loan Bank Stock
Carrying amount of financial instruments	6,163	6,390
Financial assets | Investment in Stock of Federal Reserve Bank of St. Louis
Carrying amount of financial instruments	5,018	4,363
Financial assets | Accrued interest receivable
Carrying amount of financial instruments	10,030	12,116
Deposits | Financial liabilities
Carrying amount of financial instruments	2,368,761	2,184,847
Accrued interest payable | Financial liabilities
Carrying amount of financial instruments	918	1,646
Commitments to Extend Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Letter of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Line of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial liabilities | Subordinated Debt
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial liabilities | Federal Home Loan Bank Advances
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial assets | Loans Receivable
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial assets | Cash and Cash Equivalents
Carrying amount of financial instruments	236,896	54,245
Fair Value, Inputs, Level 1 | Financial assets | Interest-bearing time deposits
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial assets | Investment in Federal Home Loan Bank Stock
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial assets | Investment in Stock of Federal Reserve Bank of St. Louis
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Financial assets | Accrued interest receivable
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Deposits | Financial liabilities
Carrying amount of financial instruments	1,775,862	1,508,740
Fair Value, Inputs, Level 1 | Accrued interest payable | Financial liabilities
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 1 | Commitments to Extend Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Letter of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Line of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Financial liabilities | Subordinated Debt
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Financial liabilities | Federal Home Loan Bank Advances
Carrying amount of financial instruments	64,088	72,136
Fair Value, Inputs, Level 2 | Financial assets | Loans Receivable
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Financial assets | Cash and Cash Equivalents
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Financial assets | Interest-bearing time deposits
Carrying amount of financial instruments	977	974
Fair Value, Inputs, Level 2 | Financial assets | Investment in Federal Home Loan Bank Stock
Carrying amount of financial instruments	6,163	6,390
Fair Value, Inputs, Level 2 | Financial assets | Investment in Stock of Federal Reserve Bank of St. Louis
Carrying amount of financial instruments	5,018	4,363
Fair Value, Inputs, Level 2 | Financial assets | Accrued interest receivable
Carrying amount of financial instruments	10,030	12,116
Fair Value, Inputs, Level 2 | Deposits | Financial liabilities
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 2 | Accrued interest payable | Financial liabilities
Carrying amount of financial instruments	918	1,646
Fair Value, Inputs, Level 2 | Commitments to Extend Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Letter of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Line of Credit
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial liabilities | Subordinated Debt
Carrying amount of financial instruments	15,016	11,511
Fair Value, Inputs, Level 3 | Financial liabilities | Federal Home Loan Bank Advances
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial assets | Loans Receivable
Carrying amount of financial instruments	2,156,852	2,143,823
Fair Value, Inputs, Level 3 | Financial assets | Cash and Cash Equivalents
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial assets | Interest-bearing time deposits
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial assets | Investment in Federal Home Loan Bank Stock
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial assets | Investment in Stock of Federal Reserve Bank of St. Louis
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Financial assets | Accrued interest receivable
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Deposits | Financial liabilities
Carrying amount of financial instruments	595,978	676,816
Fair Value, Inputs, Level 3 | Accrued interest payable | Financial liabilities
Carrying amount of financial instruments	0	0
Fair Value, Inputs, Level 3 | Commitments to Extend Credit
Carrying amount of financial instruments	$ 0	$ 0