Fair Value Measurements - Unobservable Inputs (Details) $ in Thousands	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 9,626,202	$ 9,617,248
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	9,426,489	9,472,796
First lien debt | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	9,225,290	9,275,511
First lien debt | Yield analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		9,037,133
First lien debt | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	9,219,940
First lien debt | Market quotations | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 5,350	$ 238,378
First lien debt | Low | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0639	0.0683
First lien debt | Low | Market quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.9650	0.8200
First lien debt | High | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.2062	0.1984
First lien debt | High | Market quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.9650	0.9675
First lien debt | Weighted Average | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1003	0.1013
First lien debt | Weighted Average | Market quotations | Level 3 | Broker quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.9650	0.9419
Second lien debt | Yield analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 46,678	$ 46,336
Second lien debt | Low | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1015	0.1043
Second lien debt | High | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1398	0.1425
Second lien debt | Weighted Average | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1253	0.1260
Investments in equity | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 154,521	$ 150,949
Investments in equity | Yield analysis | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	23,093	22,686
Investments in equity | Market quotations | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	105,862	105,782
Investments in equity | Option pricing model | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 25,566	$ 22,481
Investments in equity | Low | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1167	0.1131
Investments in equity | Low | Market quotations | Level 3 | Performance multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	5.70	5.50
Investments in equity | Low | Option pricing model | Level 3 | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.3000	0.3000
Investments in equity | High | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1355	0.1375
Investments in equity | High | Market quotations | Level 3 | Performance multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	39.66	29.00
Investments in equity | High | Option pricing model | Level 3 | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.5000	0.5000
Investments in equity | Weighted Average | Yield analysis | Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1288	0.1274
Investments in equity | Weighted Average | Market quotations | Level 3 | Performance multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	12.66	13.41
Investments in equity | Weighted Average | Option pricing model | Level 3 | Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.4180	0.4346