LOANS AND LEASES, NET - Direct Financing and Sales-type Leases, and Lease Receivable Maturity (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Net Investment in Lease [Abstract]
Carrying amount	$ 327,238		$ 327,238		$ 299,487
Unguaranteed residual assets	17,835		17,835		17,203
Unamortized initial direct costs	2,247		2,247		2,078
Unearned income	(36,904)		(36,904)		(35,606)
Total net investment in direct financing and sales-type leases	310,416		310,416		$ 283,162
Operating Lease, Lease Income [Abstract]
Interest income on net investments in direct financing and sales-type leases	6,116	$ 4,375	11,435	$ 8,462
Lease income from operating lease payments	9,735	11,263	19,776	22,466
Profit (loss) recorded on commencement date on sales-type leases	59	16	130	487
Other	1,687	1,831	1,756	2,581
Total leasing and equipment finance noninterest income	11,481	13,110	21,662	25,534
Total lease income	17,597	$ 17,485	33,097	$ 33,996
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Remaining in 2021	63,369		63,369
2022	108,413		108,413
2023	79,701		79,701
2024	47,563		47,563
2025	20,468		20,468
Thereafter	7,724		7,724
Equipment under leases not yet commenced	0		0
Total undiscounted future minimum lease payments receivable for direct financing and sales-type leases	327,238		327,238
Third-party residual value guarantees	0		0
Total carrying amount of direct financing and sales-type lease	$ 327,238		$ 327,238

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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 net investment in sales-type and direct financing lease.

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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.

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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 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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