LOANS AND LEASES, NET - Direct Financing and Sales-type Leases, and Lease Receivable Maturity (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020
Net Investment in Lease [Abstract]
Carrying amount	$ 297,370		$ 297,370		$ 299,487
Unguaranteed residual assets	14,770		14,770		17,203
Unamortized initial direct costs	520		520		2,078
Unearned income	(29,200)		(29,200)		(35,606)
Total net investment in direct financing and sales-type leases	283,460		283,460		$ 283,162
Operating Lease, Lease Income [Abstract]
Interest income on net investments in direct financing and sales-type leases	6,344	$ 4,496	17,779	$ 12,958
Lease income from operating lease payments	10,047	11,391	29,824	33,857
Profit (loss) recorded on commencement date on sales-type leases	85	103	215	590
Other	901	554	2,657	3,135
Total leasing and equipment finance noninterest income	11,033	12,048	32,696	37,582
Total lease income	17,377	$ 16,544	50,475	$ 50,540
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Remaining in 2021	28,766		28,766
2022	108,161		108,161
2023	80,606		80,606
2024	48,993		48,993
2025	22,798		22,798
Thereafter	8,046		8,046
Equipment under leases not yet commenced	0		0
Total undiscounted future minimum lease payments receivable for direct financing and sales-type leases	297,370		297,370
Third-party residual value guarantees	0		0
Total carrying amount of direct financing and sales-type lease	$ 297,370		$ 297,370

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Leasing and Equipment Finance, Non-interest Income

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Amount of other addition (reduction) in allowance reserve for credit loss.

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Amount of lease income from operating, direct financing, and sales-type leases. Includes, but is not limited to, variable lease payments, interest income, profit (loss) recognized at commencement, and lease payments paid and payable to lessor.

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Amount of operating lease income from lease payments paid and payable to lessor. Excludes variable lease payments not included in measurement of lease receivable.

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Amount of residual asset covered by residual value guarantee. Excludes guarantee considered to be lease payments for lessor.

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Present value of lease payments not yet received by lessor and amount expected to be derived from underlying asset, following end of lease term guaranteed by lessee or other third party unrelated to lessor, from sales-type and direct financing leases.

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in remainder of current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted lease receivable in excess of discounted receivable for sales-type and direct financing leases.

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Present value expected to be derived from underlying asset following end of lease term not guaranteed by lessee or other third party unrelated to lessor.

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