| RELATED PARTY TRANSACTIONS - Schedule of Related Party Transactions (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | ||||
|---|---|---|---|---|---|---|
| Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | |||
| Related Party Transactions [Abstract] | ||||||
| Base management fee | 1.75% | 1.75% | 1.75% | 1.75% | ||
| Average total assets subject to base management fee | $ 709,943 | $ 571,657 | $ 672,990 | $ 571,429 | ||
| Multiplied by prorated annual base management fee of 1.75% | 0.4375% | 0.4375% | 1.3125% | 1.3125% | ||
| Base management fee | [1] | $ 3,106 | $ 2,501 | $ 8,833 | $ 7,500 | |
| Portfolio company fee credit | (1,894) | (1,099) | (2,987) | (3,027) | ||
| Syndicated loan fee credit | (32) | (35) | (95) | (136) | ||
| Net Base Management Fee | 1,180 | 1,367 | 5,751 | 4,337 | ||
| Loan servicing fee | [1] | 2,069 | 1,614 | 5,866 | 4,596 | |
| Credits to base management fee – loan servicing fee | (2,069) | (1,614) | (5,866) | (4,596) | ||
| Net Loan Servicing Fee | 0 | 0 | 0 | 0 | ||
| Incentive fee | [1] | 2,919 | 1,579 | 7,508 | 5,641 | |
| Incentive fee credit | 0 | (437) | 0 | (437) | ||
| Net Incentive Fee | 2,919 | 1,142 | 7,508 | 5,204 | ||
| Credit to Fees From Adviser - other | $ (1,926) | $ (1,571) | $ (3,082) | $ (3,600) | ||
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- Definition Investment Company, Credits To Base Management Fee, Loan Servicing Fee No definition available. 
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- Definition Investment Company, Credits To Fees From Adviser, Other No definition available. 
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- Definition Investment Company , Incentive Fee Credit No definition available. 
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- Definition Investment Company , Portfolio Company Fee Credit No definition available. 
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- Definition Investment Company, Syndicated Loan Fee Credit No definition available. 
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- Definition Net Base Management Fee No definition available. 
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- Definition Net Loan Servicing Fee No definition available. 
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- Definition Net Total Incentive Fee No definition available. 
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- Definition The average carrying amount of assets managed during the period by the investment advisor on behalf of investors. No definition available. 
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- Definition Amount of expense for incentive fee based on performance under arrangement to manage operations, including, but not limited to, investment. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Expenses paid for obtaining loans which includes expenses such as application and origination fees. No definition available. 
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- Definition Base rate for management and service fees under arrangement to manage operations, including, but not limited to, investment. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Rate for management and service fees under arrangement to manage operations, including, but not limited to, investment. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of expense for investment management fee, including, but not limited to, expense in connection with research, selection, supervision, and custody of investment. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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- References No definition available. 
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