Fair Value of Investments - Schedule of Fair Value Hierarchy of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	$ 12,892,943	$ 13,010,345	[1],[2],[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	8,898,911	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	1,822,865	1,860,978
Unsecured debt investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	273,372	248,019
Preferred equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	400,625	355,261
Common equity investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,132,742	977,927
Level 1
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	1,411	816
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	1,411	816
Level 2
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	143,251	54,271
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	12,925	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	119,356	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	10,970	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]
Total Investments at fair value	12,383,853	12,666,277
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	8,885,986	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	1,703,509	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	262,402	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	400,625	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	1,131,331	977,111
Levels 1, Level 2, and Level 3
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	12,528,515	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	8,898,911	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	1,822,865	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	273,372	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	400,625	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	1,132,742	977,927
NAV
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Total Investments at fair value	$ 364,428	$ 288,981

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

[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 Facilities and CLOs. See Note 6 “Debt”.