Fair Value Measurements - Unobservable Inputs (Details) $ in Thousands	Sep. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 13,809,636	$ 13,092,518
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	13,595,554	12,976,765
First lien debt | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	13,257,332	12,714,636
First lien debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	13,102,781	12,546,382
First lien debt | Market Quotations | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	8,793	102,316
First lien debt | Asset Recoverability | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		2,059
First lien debt | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 145,758	$ 63,879
First lien debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0674	0.0700
First lien debt | Low | Market Quotations | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	97.25	97.00
First lien debt | Low | Asset Recoverability | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1033
First lien debt | Low | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	7.25	10
First lien debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1754	0.2267
First lien debt | High | Market Quotations | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	100.17	100.57
First lien debt | High | Asset Recoverability | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1092
First lien debt | High | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12	10.75
First lien debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0956	0.1015
First lien debt | Weighted Average | Market Quotations | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	99.99	100.08
First lien debt | Weighted Average | Asset Recoverability | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input		0.1036
First lien debt | Weighted Average | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.4	10.4
Second lien debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 226,249	$ 119,184
Second lien debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0826	0.0886
Second lien debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1606	0.1673
Second lien debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1001	0.1152
Unsecured debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 13,991	$ 33,521
Unsecured debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1266	0.0771
Unsecured debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1487	0.1394
Unsecured debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1456	0.1012
Investments in equity | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 97,982	$ 109,424
Investments in equity | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	20,792	21,697
Investments in equity | Market Approach | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	61,055
Investments in equity | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		69,633
Investments in equity | Market Approach | Level 3 | Transaction Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		429
Investments in equity | Asset Recoverability | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	3,263	3,166
Investments in equity | Option Pricing Model | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 12,872	$ 14,499
Investments in equity | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1199	0.0954
Investments in equity | Low | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	6.4	2.3
Investments in equity | Low | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8.5	10
Investments in equity | Low | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3200	0.2350
Investments in equity | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.2372	0.1947
Investments in equity | High | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	33.63	30
Investments in equity | High | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12	10.75
Investments in equity | High | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.7050	0.7050
Investments in equity | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1376	0.1555
Investments in equity | Weighted Average | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	13.18	10.11
Investments in equity | Weighted Average | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	10.65	10.5
Investments in equity | Weighted Average | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3600	0.3403