Loans Receivable - Non-accrual Loans and Loans 90 Days or More Past Due and Accruing (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual percent of total loans	0.17%	0.21%
Financial Asset Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 29,180	$ 34,534
Non-accrual with no ACL	906	1,308
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	11,420	16,296
Non-accrual with no ACL	906	1,308
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	5,879	5,912
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	4,635	4,691
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	906	5,693
Non-accrual with no ACL	906	1,308
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	0	0
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Commercial loans | Land - acquisition & development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	0	0
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	17,760	18,238
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	435	435
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans | Single-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	17,084	17,450
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans | Land - consumer lot loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	71	84
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans | HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	134	233
Non-accrual with no ACL	0	0
90 days or more past due and accruing	0	0
Financial Asset Originated | Consumer loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	36	36
Non-accrual with no ACL	0	0
90 days or more past due and accruing	$ 0	$ 0