Fair Value Measurements and Derivative Instruments - Significant Unobservable Inputs of the Company’s Level 3 Financial Instruments (Details) $ in Thousands	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 48,959,003	$ 30,795,693
First lien debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		28,143,451
Second lien debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		1,813,872
Structured Finance Investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		286,610
Equity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		545,918
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	37,895,208	24,598,152
Level 3 | First lien debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	35,623,823	23,046,509
Level 3 | First lien debt | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	34,814,597
Level 3 | First lien debt | EV Coverage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	29,003	22,414,991
Level 3 | First lien debt | Market quotations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 780,223	$ 631,518
Level 3 | First lien debt | Low | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.0664
Level 3 | First lien debt | Low | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.0468
Level 3 | First lien debt | Low | EV Coverage | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	7
Level 3 | First lien debt | Low | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.6697	98.00
Level 3 | First lien debt | High | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1845
Level 3 | First lien debt | High | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.1034
Level 3 | First lien debt | High | EV Coverage | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	7
Level 3 | First lien debt | High | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.9950	100.25
Level 3 | First lien debt | Weighted Average | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.0986
Level 3 | First lien debt | Weighted Average | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.0740
Level 3 | First lien debt | Weighted Average | EV Coverage | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	7
Level 3 | First lien debt | Weighted Average | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.9326	99.49
Level 3 | Second lien debt
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 1,268,919	$ 800,133
Level 3 | Second lien debt | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	918,781
Level 3 | Second lien debt | EV Coverage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		400,584
Level 3 | Second lien debt | Market quotations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 350,138	$ 399,549
Level 3 | Second lien debt | Low | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.0996
Level 3 | Second lien debt | Low | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.0815
Level 3 | Second lien debt | Low | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.6624	98.00
Level 3 | Second lien debt | High | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1410
Level 3 | Second lien debt | High | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.1304
Level 3 | Second lien debt | High | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	1.0050	101.50
Level 3 | Second lien debt | Weighted Average | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1151
Level 3 | Second lien debt | Weighted Average | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.0998
Level 3 | Second lien debt | Weighted Average | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.9035	99.07
Level 3 | Structured Finance Investments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 287,898	$ 205,592
Level 3 | Structured Finance Investments | Market quotations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 287,898	$ 205,592
Level 3 | Structured Finance Investments | Low | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	80.83	96.69
Level 3 | Structured Finance Investments | High | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	97.5	100
Level 3 | Structured Finance Investments | Weighted Average | Market quotations | Quoted price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	87.29	99.23
Level 3 | Equity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 714,568	$ 545,918
Level 3 | Equity | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	296,989
Level 3 | Equity | EV Coverage
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		236,774
Level 3 | Equity | Market quotations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value		74,022
Level 3 | Equity | Performance Multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	202,507
Level 3 | Equity | Option Pricing Model
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	25,126	22,722
Level 3 | Equity | Recent transaction
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 189,946	$ 212,400
Level 3 | Equity | Low | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1167
Level 3 | Equity | Low | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.1089
Level 3 | Equity | Low | Market quotations | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		7.25
Level 3 | Equity | Low | Performance Multiple | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	5
Level 3 | Equity | Low | Option Pricing Model | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.3000	0.3000
Level 3 | Equity | Low | Recent transaction | Transaction price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	1.0000	1.0000
Level 3 | Equity | High | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1398
Level 3 | Equity | High | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.1219
Level 3 | Equity | High | Market quotations | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		31.28
Level 3 | Equity | High | Performance Multiple | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	29.61
Level 3 | Equity | High | Option Pricing Model | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.4800	0.4900
Level 3 | Equity | High | Recent transaction | Transaction price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	1.0000	1.0000
Level 3 | Equity | Weighted Average | Discounted Cash Flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.1297
Level 3 | Equity | Weighted Average | EV Coverage | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		0.1150
Level 3 | Equity | Weighted Average | Market quotations | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input		21.38
Level 3 | Equity | Weighted Average | Performance Multiple | Market multiple
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	22.37
Level 3 | Equity | Weighted Average | Option Pricing Model | Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	0.3737	0.3824
Level 3 | Equity | Weighted Average | Recent transaction | Transaction price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement Input	1.0000	1.0000