FAIR VALUES OF FINANCIAL INSTRUMENTS - Assets Measured at Fair Value on Recurring and Non-recurring Basis (Details) - USD ($)	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between levels of fair value hierarchy	$ 0	$ 0
Available For Sale
Mortgage-backed securities available for sale, at fair value	1,017,029,000	453,607,000
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed real estate and repossessed assets, net	2,077,000	9,957,000
Level 1
Available For Sale
Total debt securities AFS	0	0
Common equities and mutual funds	12,668,000	2,969,000
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Level 2
Available For Sale
Total debt securities AFS	1,864,899,000	1,268,102,000
Common equities and mutual funds	0	0
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	0	0
Level 3
Available For Sale
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	3,616,646,000	3,307,037,000
Recurring
Available For Sale
Corporate securities	25,000,000
SBA securities	157,209,000	164,955,000
Obligations of states and political subdivisions	2,507,000	841,000
Non-bank qualified obligations of states and political subdivisions	268,295,000	323,774,000
Asset-backed securities	394,859,000	324,925,000
Mortgage-backed securities available for sale, at fair value	1,017,029,000	453,607,000
Total debt securities AFS	1,864,899,000	1,268,102,000
Common equities and mutual funds	12,668,000	2,969,000
Investment securities available for sale, at fair value	4,560,000	2,784,000
Recurring \| Level 1
Available For Sale
Corporate securities	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 available for sale, at fair value	0	0
Total debt securities AFS	0	0
Common equities and mutual funds	12,668,000	2,969,000
Investment securities available for sale, at fair value	0	0
Recurring \| Level 2
Available For Sale
Corporate securities	25,000,000
SBA securities	157,209,000	164,955,000
Obligations of states and political subdivisions	2,507,000	841,000
Non-bank qualified obligations of states and political subdivisions	268,295,000	323,774,000
Asset-backed securities	394,859,000	324,925,000
Mortgage-backed securities available for sale, at fair value	1,017,029,000	453,607,000
Total debt securities AFS	1,864,899,000	1,268,102,000
Common equities and mutual funds	0	0
Investment securities available for sale, at fair value	0	0
Recurring \| Level 3
Available For Sale
Corporate securities	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 available for sale, at fair value	0	0
Total debt securities AFS	0	0
Common equities and mutual funds	0	0
Investment securities available for sale, at fair value	0	0
Nonrecurring
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	14,852,000	19,217,000
Nonrecurring \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	3,404,000	9,240,000
Nonrecurring \| Community Banking
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	9,371,000	20,000
Nonrecurring \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	12,775,000	9,260,000
Nonrecurring \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed real estate and repossessed assets, net	2,077,000	9,957,000
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 \| Community Banking
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 real estate and repossessed assets, net	0	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 \| Community Banking
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 real estate and repossessed assets, net	0	0
Nonrecurring \| Level 3
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	14,852,000	19,217,000
Nonrecurring \| Level 3 \| National Lending
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	3,404,000	9,240,000
Nonrecurring \| Level 3 \| Community Banking
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	9,371,000	20,000
Nonrecurring \| Level 3 \| Impaired Loans
Fair value of assets measured on non-recurring basis [Abstract]
Loans and leases	12,775,000	9,260,000
Nonrecurring \| Level 3 \| Foreclosed Assets
Fair value of assets measured on non-recurring basis [Abstract]
Foreclosed real estate and repossessed assets, net	$ 2,077,000	$ 9,957,000

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

No definition available.

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- Definition

Corporate Securities Available For Sale

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No definition available.

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- References

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- Definition

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.

+ References

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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

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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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- Definition

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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- Definition

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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- Definition

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

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- Definition

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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