Borrowings - Schedule of Borrowings (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal	$ 519,250,000	$ 559,250,000	$ 81,000,000	$ 99,000,000	$ 61,000,000	$ 59,500,000	$ 0
Carrying Value	510,078,000	548,957,000
Credit Facility
Debt Instrument [Line Items]
Principal	272,000,000	337,000,000	$ 61,000,000	$ 99,000,000	$ 61,000,000
Borrowings
Debt Instrument [Line Items]
Total Commitment	797,250,000	647,250,000
Principal	519,250,000	559,250,000
Deferred Debt Cost	(9,172,000)	(10,293,000)
Carrying Value	510,078,000	548,957,000
Borrowings | Credit Facility
Debt Instrument [Line Items]
Total Commitment	550,000,000	425,000,000
Principal	272,000,000	337,000,000
Deferred Debt Cost	(4,434,000)	(4,640,000)
Carrying Value	267,566,000	332,360,000
Borrowings | April 2026 Notes
Debt Instrument [Line Items]
Total Commitment	25,000,000
Principal	25,000,000
Deferred Debt Cost	(277,000)
Carrying Value	24,723,000
Borrowings | December 2026 Notes
Debt Instrument [Line Items]
Total Commitment	70,000,000	70,000,000
Principal	70,000,000	70,000,000
Deferred Debt Cost	(573,000)	(818,000)
Carrying Value	69,427,000	69,182,000
Borrowings | July 2027 Notes
Debt Instrument [Line Items]
Total Commitment	80,500,000	80,500,000
Principal	80,500,000	80,500,000
Deferred Debt Cost	(1,924,000)	(2,380,000)
Carrying Value	78,576,000	78,120,000
Borrowings | August 2027 Notes
Debt Instrument [Line Items]
Total Commitment	20,000,000	20,000,000
Principal	20,000,000	20,000,000
Deferred Debt Cost	(511,000)	(653,000)
Carrying Value	19,489,000	19,347,000
Borrowings | December 2027 Notes
Debt Instrument [Line Items]
Total Commitment	51,750,000	51,750,000
Principal	51,750,000	51,750,000
Deferred Debt Cost	(1,453,000)	(1,802,000)
Carrying Value	$ 50,297,000	$ 49,948,000