Borrowings - 2029 Notes (Details) $ in Thousands	Jul. 24, 2024 USD ($)	Oct. 20, 2023 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)
Borrowings
Total aggregate principal amount committed/ outstanding			$ 3,005,396	$ 2,656,207
Debt			2,249,256	2,151,713
Net assets			2,442,671		$ 1,576,430
Interest expense - Revolving Credit Facility | Revolving Credit Agreement
Borrowings
Debt			451,300	396,100
Net assets	$ 500,000	$ 500,000
Amount equal to net assets	$ 660,865	$ 1,063,400
Percentage equal to net assets	65.00%	65.00%
Series C Senior Unsecured Notes 2029 | Private Placement Bonds
Borrowings
Total aggregate principal amount committed/ outstanding	$ 156,000
Interest rate	7.47%
Debt			$ 156,000	$ 156,000
Weighted average interest rate			7.50%	7.50%
Series D Senior Unsecured Notes 2029 | Private Placement Bonds
Borrowings
Total aggregate principal amount committed/ outstanding	$ 48,000
Interest rate	7.47%
Debt			$ 48,000	$ 48,000
Weighted average interest rate			7.50%	7.50%
2029 Notes | Private Placement Bonds
Borrowings
Minimum repayment of aggregate principal amount of senior notes	0.10
Debt Instrument, redemption price, percentage	100.00%
Asset coverage ratio	1.50
2029 Notes | Private Placement Bonds | Below Investment Grade Event
Borrowings
Additional interest rate	1.00%
2029 Notes | Private Placement Bonds | Secured Debt Ratio Event
Borrowings
Additional interest rate	1.50%
2029 Notes | Private Placement Bonds | Below Investment Grade Event and a Secured Debt Ratio Event
Borrowings
Additional interest rate	2.00%