FAIR VALUE OF FINANCIAL INSTRUMENTS - Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Financial assets
Debt securities held to maturity	$ 35,028	$ 38,171
Level 1
Financial assets
Cash and cash equivalents	432,598	388,038
Debt securities available for sale	0	0
Debt securities held to maturity	0	0
Common equities and mutual funds	3,545	2,874
Non-marketable equity securities	0	0
Loans held for sale	0	0
Loans and leases	0	0
Federal Reserve Bank and Federal Home Loan Bank stocks	0	0
Accrued interest receivable	22,434	17,979
Financial liabilities
Deposits	5,896,367	5,858,283
Overnight federal funds purchased	43,000
Other short- and long-term borrowings	0	0
Accrued interest payable	204	192
Level 2
Financial assets
Cash and cash equivalents	0	0
Debt securities available for sale	1,825,563	1,882,869
Debt securities held to maturity	35,028	38,171
Common equities and mutual funds	0	0
Non-marketable equity securities	14,814	15,314
Loans held for sale	24,780	21,071
Loans and leases	0	0
Federal Reserve Bank and Federal Home Loan Bank stocks	29,387	28,812
Accrued interest receivable	0	0
Financial liabilities
Deposits	6,159	7,571
Overnight federal funds purchased	0
Other short- and long-term borrowings	32,961	35,986
Accrued interest payable	0	0
Level 3
Financial assets
Cash and cash equivalents	0	0
Debt securities available for sale	0	0
Debt securities held to maturity	0	0
Common equities and mutual funds	0	0
Non-marketable equity securities	0	0
Loans held for sale	0	0
Loans and leases	3,710,718	3,525,803
Federal Reserve Bank and Federal Home Loan Bank stocks	0	0
Accrued interest receivable	0	0
Financial liabilities
Deposits	0	0
Overnight federal funds purchased	0
Other short- and long-term borrowings	0	0
Accrued interest payable	0	0
Carrying Amount
Financial assets
Cash and cash equivalents	432,598	388,038
Debt securities available for sale	1,825,563	1,882,869
Debt securities held to maturity	38,713	41,682
Common equities and mutual funds	3,545	2,874
Non-marketable equity securities	22,563	22,526
Loans held for sale	24,780	21,071
Loans and leases	3,719,898	3,529,280
Federal Reserve Bank and Federal Home Loan Bank stocks	29,387	28,812
Accrued interest receivable	22,434	17,979
Financial liabilities
Deposits	5,902,696	5,866,037
Overnight federal funds purchased	43,000
Other short- and long-term borrowings	34,543	36,028
Accrued interest payable	204	192
Estimated Fair Value
Financial assets
Cash and cash equivalents	432,598	388,038
Debt securities available for sale	1,825,563	1,882,869
Debt securities held to maturity	35,028	38,171
Common equities and mutual funds	3,545	2,874
Non-marketable equity securities	22,563	22,526
Loans held for sale	24,780	21,071
Loans and leases	3,710,718	3,525,803
Federal Reserve Bank and Federal Home Loan Bank stocks	29,387	28,812
Accrued interest receivable	22,434	17,979
Financial liabilities
Deposits	5,902,526	5,865,854
Overnight federal funds purchased	43,000
Other short- and long-term borrowings	32,961	35,986
Accrued interest payable	$ 204	$ 192

The fair value disclosure of accrued interest payable as of the balance sheet date.

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Non Marketable Equity Securities

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Fair value of Federal Home Loan Bank (FHLBank) advances carried under the fair value option.

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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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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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