Loans Held for Investment - Schedule of Past Due Status of Loans Held for Investment, Gross (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans deemed uncollectible, period of delinquency	90 days	90 days
Current	$ 852,689	$ 842,668
30-89 Days Past Due	20	7
Non-Accrual	7,250	9,407
Total Loans Held for Investment, Gross	859,959	852,082	$ 886,849
Mortgage loans, Single-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	268,811	259,984
30-89 Days Past Due	19	0
Non-Accrual	6,140	8,288
Total Loans Held for Investment, Gross	274,970	268,272	288,790
Mortgage Loans, Multi Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	488,440	483,289
30-89 Days Past Due	0	0
Non-Accrual	1,110	1,119
Total Loans Held for Investment, Gross	489,550	484,408	482,900
Mortgage loans, Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	91,779	95,279
30-89 Days Past Due	0	0
Non-Accrual	0	0
Total Loans Held for Investment, Gross	91,779	95,279	105,207
Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	2,574	3,040
30-89 Days Past Due	0	0
Non-Accrual	0	0
Total Loans Held for Investment, Gross	2,574	3,040	8,787
Mortgage Loans Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	137	139
30-89 Days Past Due	0	0
Non-Accrual	0	0
Total Loans Held for Investment, Gross	137	139	142
Commercial business loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	865	849
30-89 Days Past Due	0	0
Non-Accrual	0	0
Total Loans Held for Investment, Gross	865	849	923
Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	83	88
30-89 Days Past Due	1	7
Non-Accrual	0	0
Total Loans Held for Investment, Gross	$ 84	$ 95	$ 100
Bankruptcy [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans deemed uncollectible, period of delinquency	60 days
Troubled Debt Restructurings [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans deemed uncollectible, period of delinquency	90 days
Commercial Real Estate Or Second Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans deemed uncollectible, period of delinquency	120 days