Annual report pursuant to Section 13 and 15(d)

Fair Value of Financial Instruments - Schedule of Investments Measured at Fair Value on Recurring Basis (Details)

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Fair Value of Financial Instruments - Schedule of Investments Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($)
$ in Thousands
Dec. 31, 2022
Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 2,960,062 $ 2,432,708
Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 875 561
Private Equity Funds, Non-US    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments [1] 3,893 1,814
Including Cash And Cash Equivalents    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 2,963,955 2,434,522
Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 54,056 52,890
Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 2,741,388 2,156,709
Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 41,488 69,439
Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 92,484 115,271
Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 30,646 38,399
Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 66,027 84,460
Quoted Prices in Active Markets for Identical Assets (Level 1) | Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 66,027 84,460
Quoted Prices in Active Markets for Identical Assets (Level 1) | Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 12,625 19,765
Significant Other Observable Inputs (Level 2) | Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 0 0
Significant Other Observable Inputs (Level 2) | Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Significant Other Observable Inputs (Level 2) | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Significant Other Observable Inputs (Level 2) | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 0 0
Significant Other Observable Inputs (Level 2) | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 1,398 8,843
Significant Other Observable Inputs (Level 2) | Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 11,227 10,922
Level 3 significant unobservable inputs    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 2,881,410 2,328,483
Level 3 significant unobservable inputs | Escrow Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Other assets 875 561
Level 3 significant unobservable inputs | Unsecured Debt [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 54,056 52,890
Level 3 significant unobservable inputs | Senior Secured Debt    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 2,741,388 2,156,709
Level 3 significant unobservable inputs | Preferred Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 41,488 69,439
Level 3 significant unobservable inputs | Common Stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments 25,059 21,968
Level 3 significant unobservable inputs | Warrant [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Investments $ 19,419 $ 27,477
[1] In accordance with U.S. GAAP, certain investments are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient and are not categorized within the fair value hierarchy as per ASC 820. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the accompanying Consolidated Statement of Assets and Liabilities