Borrowings - 2029 Notes (Details) $ in Thousands	Jul. 24, 2024 USD ($)	Oct. 20, 2023 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Borrowings
Total aggregate principal amount committed/ outstanding			$ 2,656,207	$ 1,587,138
Debt			2,151,713	1,247,946
Net assets			2,059,727	1,302,667	$ 754,916	$ 369,448	$ 137,513	$ 68,745
Interest expense - Revolving Credit Facility | Revolving Credit Agreement
Borrowings
Debt			396,100	$ 240,800
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
Weighted average interest rate			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
Weighted average interest rate			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%