FAIR VALUES OF FINANCIAL INSTRUMENTS - Quantitative Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 0	$ 0
Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	4,036,490	4,223,010
Nonrecurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	7,652	21,829
Nonrecurring | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Nonrecurring | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Nonrecurring | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	7,652	21,829
Commercial finance | Nonrecurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	7,652	21,829
Commercial finance | Nonrecurring | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Commercial finance | Nonrecurring | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Commercial finance | Nonrecurring | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	7,652	21,829
Total loans and leases, net individually evaluated for credit loss | Level 3 | Valuation, Market Approach
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 7,652	21,829
Total loans and leases, net individually evaluated for credit loss | Level 3 | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Range of estimated selling cost (percentage)	3.00%
Total loans and leases, net individually evaluated for credit loss | Level 3 | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Range of estimated selling cost (percentage)	37.00%
Total loans and leases, net individually evaluated for credit loss | Nonrecurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 7,652	21,829
Total loans and leases, net individually evaluated for credit loss | Nonrecurring | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Total loans and leases, net individually evaluated for credit loss | Nonrecurring | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	0	0
Total loans and leases, net individually evaluated for credit loss | Nonrecurring | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 7,652	21,829
Foreclosed assets, net | Nonrecurring
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Foreclosed assets, net		0
Foreclosed assets, net | Nonrecurring | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Foreclosed assets, net		0
Foreclosed assets, net | Nonrecurring | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Foreclosed assets, net		0
Foreclosed assets, net | Nonrecurring | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Foreclosed assets, net		$ 0