FAIR VALUE MEASUREMENTS - Unobservable Inputs (Details) $ in Thousands	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,791,494	$ 3,193,561
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	3,686,956	3,117,354
Level 3 | First Lien Debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	3,603,209	2,979,870
Level 3 | First Lien Debt | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,597,236	$ 2,979,870
Level 3 | First Lien Debt | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0805	0.0861
Level 3 | First Lien Debt | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3406	0.2509
Level 3 | First Lien Debt | Yield Analysis | Weighted Average(3) | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1031	0.1100
Level 3 | First Lien Debt | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 5,973
Level 3 | First Lien Debt | Market Approach | Weighted Average(3) | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.065
Level 3 | Second Lien Debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 33,351	$ 96,848
Level 3 | Second Lien Debt | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 33,351	$ 96,848
Level 3 | Second Lien Debt | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1018	0.1080
Level 3 | Second Lien Debt | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1641	0.3113
Level 3 | Second Lien Debt | Yield Analysis | Weighted Average(3) | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1509	0.1437
Level 3 | Other Debt Investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 9,198	$ 2,064
Level 3 | Other Debt Investments | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 8,313
Level 3 | Other Debt Investments | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0942
Level 3 | Other Debt Investments | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1490
Level 3 | Other Debt Investments | Yield Analysis | Weighted Average(3) | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1074
Level 3 | Other Debt Investments | Income Approach | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		$ 1,894
Level 3 | Other Debt Investments | Income Approach | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1460
Level 3 | Other Debt Investments | Income Approach | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1460
Level 3 | Other Debt Investments | Income Approach | Weighted Average(3) | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1460
Level 3 | Other Debt Investments | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 885	$ 170
Level 3 | Other Debt Investments | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		9
Level 3 | Other Debt Investments | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		9
Level 3 | Other Debt Investments | Market Approach | Weighted Average(3) | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	9	9
Level 3 | Preferred equity | Income Approach | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 22,694	$ 18,758
Level 3 | Preferred equity | Income Approach | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1215	0.1219
Level 3 | Preferred equity | Income Approach | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1750	0.1568
Level 3 | Preferred equity | Income Approach | Weighted Average(3) | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1371	0.1347
Level 3 | Preferred equity | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 923	$ 1,275
Level 3 | Preferred equity | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		7.5
Level 3 | Preferred equity | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		7.5
Level 3 | Preferred equity | Market Approach | Weighted Average(3) | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.5	7.5
Level 3 | Common equity | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 14,442	$ 16,600
Level 3 | Common equity | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,139	$ 1,939
Level 3 | Common equity | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	3.9	8.1
Level 3 | Common equity | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	7.6	7.6
Level 3 | Common equity | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	18.7	18.7
Level 3 | Common equity | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12.7	9.8
Level 3 | Common equity | Market Approach | Weighted Average(3) | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	13.47	13.26
Level 3 | Common equity | Market Approach | Weighted Average(3) | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.8	8.47
Level 3 | Other Security Investments, Unsecured Debt | Yield Analysis
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 2,010