FAIR VALUE MEASUREMENTS - Unobservable Inputs (Details) $ in Thousands	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,788,178	$ 3,791,494
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	3,728,366	3,686,956
Level 3 | First Lien Debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	3,631,679	3,603,209
Level 3 | First Lien Debt | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,628,634	$ 3,597,236
Level 3 | First Lien Debt | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0585	0.0805
Level 3 | First Lien Debt | Yield Analysis | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.065
Level 3 | First Lien Debt | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.4846	0.3406
Level 3 | First Lien Debt | Yield Analysis | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0825
Level 3 | First Lien Debt | Yield Analysis | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1020	0.1031
Level 3 | First Lien Debt | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,045	$ 5,973
Level 3 | First Lien Debt | Market Approach | Weighted Average | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0652	0.065
Level 3 | Second Lien Debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 49,212	$ 33,351
Level 3 | Second Lien Debt | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 46,149	$ 33,351
Level 3 | Second Lien Debt | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1054	0.1018
Level 3 | Second Lien Debt | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.2218	0.1641
Level 3 | Second Lien Debt | Yield Analysis | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1814	0.1509
Level 3 | Second Lien Debt | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,063
Level 3 | Second Lien Debt | Market Approach | Weighted Average | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0825
Level 3 | Other Debt Investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 9,603	$ 9,198
Level 3 | Other Debt Investments | Yield Analysis | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 8,475	$ 8,313
Level 3 | Other Debt Investments | Yield Analysis | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1420	0.0942
Level 3 | Other Debt Investments | Yield Analysis | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1650	0.1490
Level 3 | Other Debt Investments | Yield Analysis | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1477	0.1074
Level 3 | Other Debt Investments | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 1,128	$ 885
Level 3 | Other Debt Investments | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.25
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 | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.32	9
Level 3 | Preferred equity | Income Approach | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 18,930	$ 22,694
Level 3 | Preferred equity | Income Approach | Low | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1184	0.1215
Level 3 | Preferred equity | Income Approach | High | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1583	0.1750
Level 3 | Preferred equity | Income Approach | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1284	0.1371
Level 3 | Preferred equity | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 4,266	$ 923
Level 3 | Preferred equity | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.25
Level 3 | Preferred equity | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	15.75
Level 3 | Preferred equity | Market Approach | Weighted Average | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	13.81	8.5
Level 3 | Common equity | Market Approach | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 11,705	$ 14,442
Level 3 | Common equity | Market Approach | Revenue Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 2,971	$ 3,139
Level 3 | Common equity | Market Approach | Low | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	3.9	3.9
Level 3 | Common equity | Market Approach | Low | Revenue Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	9	7.6
Level 3 | Common equity | Market Approach | High | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	18.6	18.7
Level 3 | Common equity | Market Approach | High | Revenue Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	22.5	12.7
Level 3 | Common equity | Market Approach | Weighted Average | EBITDA Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12.17	13.47
Level 3 | Common equity | Market Approach | Weighted Average | Revenue Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12.71	8.8
Level 3 | Other Security Investments, Unsecured Debt | Yield Analysis
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,000	$ 2,010