Fair Value Measurements - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	$ 13,809,636	$ 13,092,518
First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	13,469,751	12,830,389
Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	226,249	119,184
Unsecured debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	13,991	33,521
Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	99,645	109,424
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	1,663	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 | Unsecured 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	1,663	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	212,419	115,753
Level 2 | First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	212,419	115,753
Level 2 | Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	0	0
Level 2 | Unsecured 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	13,595,554	12,976,765
Level 3 | First lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	13,257,332	12,714,636
Level 3 | Second lien debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	226,249	119,184
Level 3 | Unsecured debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	13,991	33,521
Level 3 | Investments in equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	$ 97,982	$ 109,424