Investments - Schedule of Investments Excluding Investments in Money Market Funds (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule Of Investments [Line Items]
Cost	$ 3,640,329	$ 3,573,791
Fair Value	3,442,129	3,414,329
1st Lien/Senior Secured Debt
Schedule Of Investments [Line Items]
Cost	3,273,037	3,209,938
Fair Value	3,153,300	3,107,469
1st Lien/Last-Out Unitranche
Schedule Of Investments [Line Items]
Cost	166,123	148,067
Fair Value	163,304	144,743
2nd Lien/Senior Secured Debt
Schedule Of Investments [Line Items]
Cost	55,656	84,626
Fair Value	42,885	66,562
Unsecured Debt
Schedule Of Investments [Line Items]
Cost	38,771	27,930
Fair Value	16,314	27,314
Preferred Stock
Schedule Of Investments [Line Items]
Cost	35,413	44,198
Fair Value	30,147	37,296
Common Stock
Schedule Of Investments [Line Items]
Cost	69,480	57,183
Fair Value	35,791	30,701
Warrants
Schedule Of Investments [Line Items]
Cost	1,849	1,849
Fair Value	$ 388	$ 244