LOANS HELD FOR INVESTMENT, NET - Performance of Modified Loans, After 12 Months (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	$ 112,989	$ 37,747
Current
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	82,716	36,849
30 to 59 Days Past Due
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	1,001
60 to 89 Days Past Due
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	27,599
Non-Accrual
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	1,673	898
Business Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	19,339	10,188
Business Loans | Current
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	17,565	9,290
Business Loans | 30 to 59 Days Past Due
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	1,001
Business Loans | Non-Accrual
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	773	898
One-to-Four Family Residential and Cooperative/Condominium Apartment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	3,749	2,854
One-to-Four Family Residential and Cooperative/Condominium Apartment | Current
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	2,849	2,854
One-to-Four Family Residential and Cooperative/Condominium Apartment | Non-Accrual
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	900
Multifamily Residential and Residential Mixed-Use
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	34,095
Multifamily Residential and Residential Mixed-Use | Current
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	6,496
Multifamily Residential and Residential Mixed-Use | 60 to 89 Days Past Due
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	27,599
Non-Owner-Occupied Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	55,806	24,705
Non-Owner-Occupied Commercial Real Estate | Current
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans that defaulted during the quarter and were modified in the 12 months before default to borrowers experiencing financial difficulty	$ 55,806	$ 24,705