FAIR VALUES OF FINANCIAL INSTRUMENTS - Assets Measured at Fair Value on Recurring and Non-recurring Basis (Details) - USD ($)	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between levels of fair value hierarchy	$ 0	$ 0
Level 1
Securities AFS
Total debt securities AFS	0	0
Common equities and mutual funds	3,378,000	2,874,000
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Level 2
Securities AFS
Total debt securities AFS	1,804,228,000	1,882,869,000
Common equities and mutual funds	0	0
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Level 3
Securities AFS
Total debt securities AFS	0	0
Common equities and mutual funds	0	0
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	4,223,010,000	3,525,803,000
Recurring
Securities AFS
Corporate securities	18,250,000	22,187,000
SBA securities	85,242,000	97,768,000
Obligations of states and political subdivisions	2,289,000	2,344,000
Non-bank qualified obligations of states and political subdivisions	226,723,000	263,783,000
Asset-backed securities	246,199,000	147,790,000
Mortgage-backed securities	1,225,525,000	1,348,997,000
Total debt securities AFS	1,804,228,000	1,882,869,000
Common equities and mutual funds	3,378,000	2,874,000
Non-marketable equity securities	8,389,000	7,212,000
Recurring \| Level 1
Securities AFS
Corporate securities	0	0
SBA securities	0	0
Obligations of states and political subdivisions	0	0
Non-bank qualified obligations of states and political subdivisions	0	0
Asset-backed securities	0	0
Mortgage-backed securities	0	0
Total debt securities AFS	0	0
Common equities and mutual funds	3,378,000	2,874,000
Non-marketable equity securities	0	0
Recurring \| Level 2
Securities AFS
Corporate securities	18,250,000	22,187,000
SBA securities	85,242,000	97,768,000
Obligations of states and political subdivisions	2,289,000	2,344,000
Non-bank qualified obligations of states and political subdivisions	226,723,000	263,783,000
Asset-backed securities	246,199,000	147,790,000
Mortgage-backed securities	1,225,525,000	1,348,997,000
Total debt securities AFS	1,804,228,000	1,882,869,000
Common equities and mutual funds	0	0
Non-marketable equity securities	0	0
Recurring \| Level 3
Securities AFS
Corporate securities	0	0
SBA securities	0	0
Obligations of states and political subdivisions	0	0
Non-bank qualified obligations of states and political subdivisions	0	0
Asset-backed securities	0	0
Mortgage-backed securities	0	0
Total debt securities AFS	0	0
Common equities and mutual funds	0	0
Non-marketable equity securities	0	0
Nonrecurring
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	21,829,000	1,576,000
Nonrecurring \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	21,829,000	1,575,000
Nonrecurring \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	21,829,000	1,575,000
Nonrecurring \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed assets, net		1,000
Nonrecurring \| Level 1
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 1 \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 1 \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 1 \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed assets, net		0
Nonrecurring \| Level 2
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 2 \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 2 \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Nonrecurring \| Level 2 \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed assets, net		0
Nonrecurring \| Level 3
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	21,829,000	1,576,000
Nonrecurring \| Level 3 \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	21,829,000	1,575,000
Nonrecurring \| Level 3 \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	$ 21,829,000	1,575,000
Nonrecurring \| Level 3 \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed assets, net		$ 1,000

Fair value of asset backed securities investments classified as available for sale.

No definition available.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents common equities and mutual funds as of the balance sheet date which have been categorized as available-for-sale.

+ References

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Corporate Securities Available For Sale

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Fair Value, Assets, total transfer amount between any of the levels 1, 2 or 3.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents non-bank qualified obligations of states and political subdivision as of the balance sheet date which have been categorized as available-for-sale.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents obligations of states and political subdivision as of the balance sheet date which have been categorized as available-for-sale.

+ References

No definition available.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents debt securities issued by the Small Business Administration (SBA) as of the balance sheet date which have been categorized as available-for-sale.

+ References

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

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No definition available.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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