Fair Value Measurements - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	$ 9,500,000	$ 9,617,248
First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	9,347,664	9,419,963
Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	40,715	46,336
Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	111,621	150,949
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 1 | First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 1 | Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 1 | Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	181,372	144,452
Level 2 | First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	181,372	144,452
Level 2 | Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 2 | Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	9,318,628	9,472,796
Level 3 | First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	9,166,292	9,275,511
Level 3 | Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	40,715	46,336
Level 3 | Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	$ 111,621	$ 150,949