Agreements and Related Party Transactions - Summary of Investments in Controlled Affiliates (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	$ 1,582,075
Fair Value, Ending balance	1,591,433
Controlled Affiliated
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	63,919	$ 11,375
Gross Additions	1,608	55,847
Gross Reductions	(8,656)	(1,760)
Net Realized Gains/ (Losses)	6,443
Change in Unrealized Gains/ (Losses)	(15,231)	(3,482)
Fair Value, Ending balance	48,083	61,980
Dividend, Interest, PIK and Other Income	8,513	8,820
Controlled Affiliated | Envocore LLC
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	10,375	11,375
Gross Additions	1,608	241
Gross Reductions	(677)	(52)
Change in Unrealized Gains/ (Losses)	(2,387)	(525)
Fair Value, Ending balance	8,919	11,039
Dividend, Interest, PIK and Other Income	456	660
Controlled Affiliated | First Eagle Logan JV, LLC
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	39,004
Gross Additions		44,768
Gross Reductions	(2,560)	(683)
Change in Unrealized Gains/ (Losses)	(5,046)	(5,383)
Fair Value, Ending balance	31,398	38,702
Dividend, Interest, PIK and Other Income	7,624	8,160
Controlled Affiliated | Loadmaster Derrick & Equipment, Inc.
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	6,287
Gross Additions		1,807
Gross Reductions	(3,750)
Net Realized Gains/ (Losses)	6,443
Change in Unrealized Gains/ (Losses)	(4,807)	1,859
Fair Value, Ending balance	4,173	3,666
Dividend, Interest, PIK and Other Income	433
Controlled Affiliated | OEM Group, LLC
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	8,253
Gross Additions		9,031
Gross Reductions	(1,669)	(1,025)
Change in Unrealized Gains/ (Losses)	(2,991)	567
Fair Value, Ending balance	$ 3,593	$ 8,573