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DISTRIBUTIONS TO COMMON STOCKHOLDERS - Adjustments for Book-tax Differences to Reflect Tax Character (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2023 | Sep. 30, 2022
Undistributed net investment income |  |
Investment Company, Changes in Net Assets [Line Items] |  |
Tax reclassification, increase (decrease) | $ (373) | $ (5,606)
Accumulated net realized losses |  |
Investment Company, Changes in Net Assets [Line Items] |  |
Tax reclassification, increase (decrease) | 373 | 7,013
Capital in excess of par value |  |
Investment Company, Changes in Net Assets [Line Items] |  |
Tax reclassification, increase (decrease) | $ 0 | $ (1,407)

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