Debt - Outstanding borrowings (Details) - USD ($)		Jun. 30, 2023	Dec. 31, 2022	Nov. 30, 2021	Oct. 13, 2021	Mar. 10, 2021
Debt
Total aggregate principal amount committed		$ 1,617,500,000	$ 1,667,500,000
Principal amount outstanding		1,498,500,000	1,395,500,000
Carrying value	[1]	1,489,607,000	1,385,303,000
2019-1 Notes
Debt
Total aggregate principal amount committed		352,500,000	352,500,000	$ 410,000,000
Principal amount outstanding		352,500,000	352,500,000
Carrying value	[1]	351,163,000	351,099,000
Revolving Advisor Loan
Debt
Total aggregate principal amount committed			50,000
March 2026 Notes
Debt
Total aggregate principal amount committed		300,000,000	300,000,000			$ 300,000,000
Principal amount outstanding		300,000,000	300,000,000
Carrying value	[1]	296,952,000	296,392,000
October 2026 Notes
Debt
Total aggregate principal amount committed		300,000,000	300,000,000		$ 300,000,000
Principal amount outstanding		300,000,000	300,000,000
Carrying value	[1]	295,492,000	294,812,000
Sumitomo Credit Facility
Debt
Total aggregate principal amount committed	[2]	665,000,000	665,000,000
Principal amount outstanding	[2]	546,000,000	443,000,000
Carrying value	[1],[2]	$ 546,000,000	$ 443,000,000

[1] Carrying value represents aggregate principal amount outstanding less unamortized debt issuance costs.

[2] On January 26, 2022, Gale Aviation (Offshore) Co investment, a controlled affiliate investment of the Company, entered into a letter of credit agreement with Sumitomo Mitsui Banking Corporation for $14.7 million. As of June 30, 2023, $14.7 million is outstanding on the letter of credit and the amount has been drawn against the total aggregate principal amount committed of the Sumitomo Credit Facility.