SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands |
12 Months Ended | |||||||||||||||||||
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Mar. 31, 2026
USD ($)
segment
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Mar. 31, 2025
USD ($)
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| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Cost | $ 1,052,848 | [1] | $ 939,066 | [2] | ||||||||||||||||
| Fair Value | $ 1,309,248 | [1] | 979,320 | [2] | ||||||||||||||||
| Number of reportable segments | segment | 1 | |||||||||||||||||||
| B+T Group Acquisition, Inc., Edge Adhesives Holdings Inc., And J.R. Hobbs Co | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Cost | $ 40,300 | |||||||||||||||||||
| Cost percentage | 5.40% | |||||||||||||||||||
| Fair Value | $ 9,100 | |||||||||||||||||||
| Fair value percentage | 1.40% | |||||||||||||||||||
| Edge Adhesives Holdings, Inc., J.R. Hobbs Co. and The Mountain | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Cost | $ 90,200 | |||||||||||||||||||
| Cost percentage | 13.10% | |||||||||||||||||||
| Fair Value | $ 50,900 | |||||||||||||||||||
| Fair value percentage | 8.20% | |||||||||||||||||||
| Non-Control/Non-Affiliate investments | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Investment owned, percent of voting securities | 5.00% | |||||||||||||||||||
| Cost | $ 711,741 | [3] | $ 562,371 | [4] | ||||||||||||||||
| Fair Value | 983,959 | [3] | 648,589 | [4] | ||||||||||||||||
| Affiliate investments | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Cost | 323,698 | [5] | 359,286 | [6] | ||||||||||||||||
| Fair Value | $ 324,676 | [5] | 330,388 | [6] | ||||||||||||||||
| Affiliate investments | Minimum | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Investment owned, percent of voting securities | 5.00% | |||||||||||||||||||
| Affiliate investments | Maximum | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Investment owned, percent of voting securities | 25.00% | |||||||||||||||||||
| Control investments | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Investment owned, percent of voting securities | 25.00% | |||||||||||||||||||
| Cost | $ 17,409 | [7] | 17,409 | [8] | ||||||||||||||||
| Fair Value | $ 613 | [7] | $ 343 | [8] | ||||||||||||||||
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- Definition Investment Owned, Percent of Cost Basis No definition available.
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- Definition Investment Owned, Percent of Fair Value No definition available.
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- Definition Investment Owned, Percent of Voting Securities No definition available.
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- Definition Cost of the investment. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Fair value of investment in security owned. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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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. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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