Fair Value of Financial Instruments - Fair Value of Level 3 Investments at Fair Value Significant Unobservable Inputs Used in Valuations (Details) - Level 3 $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 4,274,058	$ 3,096,465
Income Approach | First-lien Debt Investments | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 3,979,498	$ 2,848,805
Income Approach | First-lien Debt Investments | Discount Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.094	0.087
Income Approach | First-lien Debt Investments | Discount Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.173	0.164
Income Approach | First-lien Debt Investments | Discount Rate | Weighted Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.125	0.128
Income Approach | Second-lien Debt Investments | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 89,086	$ 79,091
Income Approach | Second-lien Debt Investments | Discount Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.175	0.217
Income Approach | Second-lien Debt Investments | Discount Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.22	0.217
Income Approach | Second-lien Debt Investments | Discount Rate | Weighted Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.215	0.217
Income Approach | Mezzanine Debt Investments | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 111,081	$ 105,918
Income Approach | Mezzanine Debt Investments | Discount Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.137	0.15
Income Approach | Mezzanine Debt Investments | Discount Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.137	0.15
Income Approach | Mezzanine Debt Investments | Discount Rate | Weighted Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.137	0.15
Market Multiple | Equity and Other Investments | Comparable Multiple
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 94,393	$ 62,651
Market Multiple | Equity and Other Investments | Comparable Multiple | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.026	0.026
Market Multiple | Equity and Other Investments | Comparable Multiple | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.20	0.161
Market Multiple | Equity and Other Investments | Comparable Multiple | Weighted Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Investment measurement input	0.103	0.102