Fair Value of Investments - Schedule of Fair Value Hierarchy of Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023		Dec. 31, 2022
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	$ 12,713,348	[1],[2],[3],[4]	$ 13,010,345	[5],[6],[7]
Interest rate swaps	$ 0		0
Derivative Liability, Statement Of Financial Position, Extensible Enumeration, Not Disclosed Flag	Interest rate swaps
First-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	$ 8,660,754		9,279,179
Second-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,774,984		1,860,978
Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	292,751		248,019
Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	433,297		355,261
Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,208,776		977,927
Levels 1, Level 2, and Level 3
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash (including restricted and foreign cash)	659,658		445,087
Total Investments at fair value	12,370,562		12,721,364
Levels 1, Level 2, and Level 3 | First-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	8,660,754		9,279,179
Levels 1, Level 2, and Level 3 | Second-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,774,984		1,860,978
Levels 1, Level 2, and Level 3 | Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	292,751		248,019
Levels 1, Level 2, and Level 3 | Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	433,297		355,261
Levels 1, Level 2, and Level 3 | Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,208,776		977,927
Level 1
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash (including restricted and foreign cash)	659,658		445,087
Total Investments at fair value	1,093		816
Interest rate swaps	0		0
Level 1 | First-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 1 | Second-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 1 | Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 1 | Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 1 | Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,093		816
Level 2
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash (including restricted and foreign cash)	0		0
Total Investments at fair value	111,508		54,271
Interest rate swaps	0		0
Level 2 | First-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 2 | Second-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	99,715		43,692
Level 2 | Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	11,793		10,579
Level 2 | Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 2 | Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	0		0
Level 3
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash (including restricted and foreign cash)	0		0
Total Investments at fair value	12,257,961		12,666,277
Interest rate swaps	(45,656)		(69,472)
Level 3 | First-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	8,660,754		9,279,179
Level 3 | Second-lien senior secured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,675,269		1,817,286
Level 3 | Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	280,958		237,440
Level 3 | Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	433,297		355,261
Level 3 | Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,207,683		977,111
NAV
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	$ 342,786		$ 288,981

[1] Unless otherwise indicated, loan contains a variable rate structure and may be subject to an interest rate floor. Variable rate loans bear interest at a rate that may be determined by reference to either the Secured Overnight Financing Rate ("SOFR" or "S," which can include one-, three- or six- month SOFR), Euro Interbank Offered Rate (“EURIBOR”), Great Britain Pound London Interbank Offered Rate (“GBPLIBOR” or “G”, which can include three- or six-month GBPLIBOR), SONIA ("SONIA” or "SA") or an alternate base rate (which can include the Federal Funds Effective Rate or the Prime Rate), at the borrower’s option, and which reset periodically based on the terms of the loan agreement.

[2] Unless otherwise indicated, all investments are considered Level 3 investments.

[3] Unless otherwise indicated, the Company’s portfolio companies are pledged as collateral supporting the amounts outstanding under the Revolving Credit Facility, SPV Asset Facility and CLOs. See Note 6 “Debt”.

[4] Certain portfolio company investments are subject to contractual restrictions on sales. Refer to footnote 26 for additional information on our restricted securities.

[5] Certain portfolio company investments are subject to contractual restrictions on sales. Refer to footnote 28 for additional information on our restricted securities.

[6] Unless otherwise indicated, all investments are considered Level 3 investments.

[7] Unless otherwise indicated, the Company’s portfolio companies are pledged as collateral supporting the amounts outstanding under the Revolving Credit Facility, SPV Asset Facilities and CLOs. See Note 6 “Debt”.