Fair Value Measurement - Summary of Assets Categorized Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	$ 3,618,060	$ 3,478,443
Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized appreciation (depreciation) on foreign currency forward contracts	111	100
1st Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	3,199,586	2,945,368
1st Lien/Last-Out Unitranche
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	118,138	162,532
2nd Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	217,105	283,521
Unsecured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	7,661	1,733
Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	41,929	52,655
Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	33,173	30,784
Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	468	1,850
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	944	684
Level 1 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	944	684
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	139,815	207,099
Level 2 | Foreign Currency Forward Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized appreciation (depreciation) on foreign currency forward contracts	111	100
Level 2 | 1st Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	86,405	102,358
Level 2 | 2nd Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	53,410	104,741
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	3,477,301	3,270,660
Level 3 | 1st Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	3,113,181	2,843,010
Level 3 | 1st Lien/Last-Out Unitranche
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	118,138	162,532
Level 3 | 2nd Lien/Senior Secured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	163,695	178,780
Level 3 | Unsecured Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	7,661	1,733
Level 3 | Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	41,929	52,655
Level 3 | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	32,229	30,100
Level 3 | Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt investments, Fair Value	$ 468	$ 1,850