FAIR VALUE HIERARCHY FOR INVESTMENTS—PORTFOLIO COMPOSITION - Schedule of Investments (Details) $ in Thousands |
3 Months Ended | 12 Months Ended | ||||||||||||||||||
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Mar. 31, 2026
USD ($)
company
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Dec. 31, 2025
USD ($)
company
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| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Fair value | $ 5,674,751 | [1],[2],[3] | $ 5,518,117 | [4],[5],[6] | ||||||||||||||||
| Cost | 4,933,484 | [1],[3],[7] | 4,724,528 | [4],[6],[8] | ||||||||||||||||
| Non-accrual Status | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Fair value | 68,300 | 56,300 | ||||||||||||||||||
| Cost | $ 199,100 | $ 155,300 | ||||||||||||||||||
| Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 100.00% | 100.00% | ||||||||||||||||||
| Investment Owned, At Cost | Investment Type Concentration Risk | Non-accrual Status | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 4.00% | 3.30% | ||||||||||||||||||
| Equity | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 18.00% | 18.60% | ||||||||||||||||||
| First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 81.20% | 80.90% | ||||||||||||||||||
| LMM portfolio investments | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Number of portfolio companies | company | 93 | 92 | ||||||||||||||||||
| Fair value | $ 3,227,400 | $ 3,057,000 | ||||||||||||||||||
| Cost | $ 2,577,000 | $ 2,419,300 | ||||||||||||||||||
| Weighted-average annual effective yield (as a percent) | 12.60% | 12.50% | ||||||||||||||||||
| Average EBITDA | $ 11,200 | $ 11,100 | ||||||||||||||||||
| Diluted equity ownership (as a percent) | 36.00% | 37.00% | ||||||||||||||||||
| Investment company, number of companies within portfolio excluded from EBITDA calculation | company | 5 | |||||||||||||||||||
| LMM portfolio investments | Non-accrual Status | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Weighted-average annual effective yield (as a percent) | 12.10% | 12.00% | ||||||||||||||||||
| LMM portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 72.00% | 71.20% | ||||||||||||||||||
| LMM portfolio investments | Equity | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 28.00% | 28.80% | ||||||||||||||||||
| LMM portfolio investments | First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 99.40% | 99.40% | ||||||||||||||||||
| Private Loan portfolio investments | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Number of portfolio companies | company | 85 | 86 | ||||||||||||||||||
| Fair value | $ 1,993,900 | $ 1,988,400 | ||||||||||||||||||
| Cost | $ 2,057,000 | $ 2,014,100 | ||||||||||||||||||
| Weighted-average annual effective yield (as a percent) | 10.30% | 10.50% | ||||||||||||||||||
| Average EBITDA | $ 34,200 | $ 33,900 | ||||||||||||||||||
| Investment company, number of companies within portfolio excluded from EBITDA calculation | company | 6 | |||||||||||||||||||
| Private Loan portfolio investments | Non-accrual Status | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Weighted-average annual effective yield (as a percent) | 9.70% | 10.10% | ||||||||||||||||||
| Private Loan portfolio investments | Debt | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 94.50% | 93.50% | ||||||||||||||||||
| Private Loan portfolio investments | Equity | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 5.50% | 6.50% | ||||||||||||||||||
| Private Loan portfolio investments | First lien debt | Investment Owned, At Cost | Investment Type Concentration Risk | ||||||||||||||||||||
| Summary of Investment Holdings [Line Items] | ||||||||||||||||||||
| Concentration risk (as a percent) | 99.30% | 99.90% | ||||||||||||||||||
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