Fair Value of Financial Instruments - Fair Value of Level 3 Investments at Fair Value and Significant Unobservable Inputs Used in Valuations (Details) - Level 3 $ in Thousands	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 3,293,341	$ 3,208,957
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	$ 3,074,994	$ 2,993,786
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	0.091	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	0.20	0.179
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	0.137	0.142
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	$ 27,993	$ 35,975
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	0.149	0.153
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	0.206	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	0.166	0.176
Income Approach | Mezzanine Debt Investments | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair Value	$ 42,282	$ 38,865
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	0.136	0.146
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	0.225	0.225
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	0.145	0.154
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	$ 148,072	$ 140,331
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	0.02	0.02
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	0.192
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	0.071	0.067