v3.26.1
Fair Value of Investments - Quantitative information about the significant unobservable inputs of Level 3 investments (Details)
$ in Thousands
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 2,960,692 $ 2,882,954 [1],[2],[3],[4]
Level 3    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 2,763,239 2,684,098
First Lien Loans    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 2,617,370 2,549,002
First Lien Loans | Level 3    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 2,507,023 2,437,356
First Lien Loans | Level 3 | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 2,050,419 1,991,420
First Lien Loans | Level 3 | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 410,077 423,921
First Lien Loans | Level 3 | Recovery Analysis | Recovery Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 46,527 $ 22,015
Debt   5.8
First Lien Loans | Level 3 | Minimum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 5.3 5.5
First Lien Loans | Level 3 | Minimum [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 98.1 97
First Lien Loans | Level 3 | Minimum [Member] | Recovery Analysis | Recovery Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 0.3  
First Lien Loans | Level 3 | Maximum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 16 15.4
First Lien Loans | Level 3 | Maximum [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 100 100
First Lien Loans | Level 3 | Maximum [Member] | Recovery Analysis | Recovery Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 6  
First Lien Loans | Level 3 | Weighted Average [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 9.7 9
First Lien Loans | Level 3 | Weighted Average [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 99.2 99.2
First Lien Loans | Level 3 | Weighted Average [Member] | Recovery Analysis | Recovery Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 3  
Second Lien Loans    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 129,726 $ 133,093
Second Lien Loans | Level 3    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 81,694 73,430
Second Lien Loans | Level 3 | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 74,900 $ 73,430
Second Lien Loans | Level 3 | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 6,794  
Debt 99.5  
Second Lien Loans | Level 3 | Minimum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 8.6 8.1
Second Lien Loans | Level 3 | Maximum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 24.6 20.6
Second Lien Loans | Level 3 | Weighted Average [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 13.6 12.1
Unsecured Notes    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 155,317 $ 138,583
Unsecured Notes | Level 3    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 131,894 122,502
Unsecured Notes | Level 3 | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 117,225 104,413
Unsecured Notes | Level 3 | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 14,669 $ 937
Debt   174
Unsecured Notes | Level 3 | Minimum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 6.6 6.5
Unsecured Notes | Level 3 | Minimum [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 98  
Unsecured Notes | Level 3 | Maximum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 14.4 15.5
Unsecured Notes | Level 3 | Maximum [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 100  
Unsecured Notes | Level 3 | Weighted Average [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 12.2 11.6
Unsecured Notes | Level 3 | Weighted Average [Member] | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Debt 98.2  
Unsecured Notes One | Level 3 | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value   $ 17,152
Debt   98.5
Preferred Equity    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 31,484 $ 40,166
Preferred Equity | Level 3    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 31,484 40,166
Preferred Equity | Level 3 | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value 26,611 36,224
Preferred Equity | Level 3 | Market Transaction | Market Transaction    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 1,149  
Equity investments 100  
Preferred Equity | Level 3 | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 3,724 $ 3,942
Preferred Equity | Level 3 | Minimum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 13.1 13.1
Preferred Equity | Level 3 | Minimum [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 12.5 13
Preferred Equity | Level 3 | Maximum [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 15.1 14.9
Preferred Equity | Level 3 | Maximum [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 17.3 19
Preferred Equity | Level 3 | Weighted Average [Member] | Discounted Cash Flow | Discount Rate    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 14.4 14.2
Preferred Equity | Level 3 | Weighted Average [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 16.6 18.2
Common Equity & Warrants    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 28,919 $ 22,110
Common Equity & Warrants | Level 3 | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Fair Value $ 11,144 $ 10,644
Common Equity & Warrants | Level 3 | Minimum [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 7.3 7
Common Equity & Warrants | Level 3 | Maximum [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 21 21.5
Common Equity & Warrants | Level 3 | Weighted Average [Member] | Enterprise Value Analysis | EBITDA Multiple    
Quantitative information about the significant unobservable inputs of Level 3 investments    
Equity investments 17.6 17
[1] All investments were qualifying assets as defined under Section 55(a) of the Investment Company Act of 1940, as amended (the "1940 Act"), except for ALP CFO LP 2024-1, Apex Group Treasury LLC, Barings Middle Market CLO Ltd., Best Egg Asset Structured Pass Through Master Trust, Churchill Middle Market CLO Ltd., Claros Mortgage Trust, Inc., Coller Capital, Exeter Short Term Funding LLC, Inizio Group Limited, Ivy Hill Asset Management, Ivy Hill Middle Market Credit Fund XII Ltd, LD Holdings Group LLC., MC CIF Wealth Management (UK) Ltd. New Mountain Guardian IV Income Rated Feeder II, Ltd., New Mountain Guardian IV Rated Feeder III, LTD., and Syntax Systems Limited.
[2] All of the Company’s investments are domiciled in the United States except for Apex Group Treasury LLC, Barings Middle Market CLO Ltd., Inizio Group Limited, MC CIF Wealth Management Ltd, Flow Traders Holding LLC, New Mountain Guardian IV Income Rated Feeder II Ltd & New Mountain Guardian IV Rated Feeder III Ltd, and Syntax Systems Limited, which are domiciled in Ireland, the Cayman Islands, United Kingdom, United Kingdom, Bermuda, Bermuda, and Canada, respectively.
[3] As of December 31, 2025, all investments are pledged as collateral unless otherwise stated.
[4] Unless otherwise indicated, all securities are valued using significant unobservable inputs, which are categorized as Level 3 assets under the definition of ASC 820 fair value hierarchy.