Fair Value Measurements - Unobservable Inputs (Details) $ in Thousands	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 11,978,616	$ 9,868,440
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	11,871,994	9,710,582
First lien debt | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	11,712,831	9,564,203
First lien debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	11,480,452	9,533,700
First lien debt | Market Approach | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	65,163
First lien debt | Asset Recoverability | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	70,858	$ 30,503
First lien debt | Market Quotations | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 96,358
First lien debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0462	0.0768
First lien debt | Low | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	10.7
First lien debt | Low | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	8	10.5
First lien debt | Low | Market Quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	96.75
First lien debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1750	0.3089
First lien debt | High | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	10.7
First lien debt | High | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	11.25	10.5
First lien debt | High | Market Quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	99.5
First lien debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0941	0.1031
First lien debt | Weighted Average | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	10.7
First lien debt | Weighted Average | Asset Recoverability | Level 3 | Market Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	9.72	10.5
First lien debt | Weighted Average | Market Quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	98.92
Second lien debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 42,415	$ 41,515
Second lien debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0894	0.1018
Second lien debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1614	0.1438
Second lien debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1269	0.1269
Unsecured debt | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 12,724	$ 9,924
Unsecured debt | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1277	0.1490
Unsecured debt | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1395	0.1490
Unsecured debt | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1379	0.1490
Investments in equity | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 104,024	$ 94,940
Investments in equity | Yield Analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	25,750	6,402
Investments in equity | Market Approach | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	63,431	60,007
Investments in equity | Option Pricing Model | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 14,843	$ 28,531
Investments in equity | Low | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0874	0.1075
Investments in equity | Low | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	6.55	6.40
Investments in equity | Low | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3200	0.3200
Investments in equity | High | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1791	0.1792
Investments in equity | High | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	31.5	30.00
Investments in equity | High | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.5600	0.5500
Investments in equity | Weighted Average | Yield Analysis | Level 3 | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1170	0.1417
Investments in equity | Weighted Average | Market Approach | Level 3 | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12.39	11.47
Investments in equity | Weighted Average | Option Pricing Model | Level 3 | Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3832	0.4286