Investments at Fair Value - Summary of Investments at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 4,197,705	$ 3,037,826
Fair Value	4,277,564	3,099,151
Net Unrealized Gain (Loss)	79,859	61,325
First-lien Debt Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,910,177	2,792,928
Fair Value	3,981,621	2,850,885
Net Unrealized Gain (Loss)	71,444	57,957
Second-lien Debt Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	88,117	77,895
Fair Value	89,086	79,091
Net Unrealized Gain (Loss)	969	1,196
Mezzanine Debt Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	108,501	104,352
Fair Value	112,464	106,524
Net Unrealized Gain (Loss)	3,963	2,172
Equity and Other Investments
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	90,910	62,651
Fair Value	94,393	$ 62,651
Net Unrealized Gain (Loss)	$ 3,483