Loans Receivable - Loans on Non-accrual Status (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual percent of total loans	0.29%	0.21%
Financial Asset Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual	$ 50,422	$ 34,534
Non-accrual with no ACL	0	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	34,644	16,296
Non-accrual with no ACL	0	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	5,127	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	23,435	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	6,082	5,693
Non-accrual with no ACL	0	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	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	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	15,778	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	88	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	14,918	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	9	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	736	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	27	36
Non-accrual with no ACL	0	0
90 days or more past due and accruing	$ 0	$ 0