DERIVATIVES - (Derivative position) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount, derivative asset		$ 700,000
Interest rate swaps and caps related to customer deposits and borrowings
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount, derivative asset		$ 700,000
Derivatives designated as hedges | Interest rate swaps and caps related to customer deposits and borrowings
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount, derivative asset	$ 700,000
Fair Value, Other Assets	1,530
Fair Value, Other Liabilities	4,880
Derivatives not designated as hedges | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount, derivative asset	69,000
Fair Value, Other Assets	1,157
Fair Value, Other Liabilities	$ 1,157