Agreements and Related Party Transactions - Summary of Investments in Controlled Affiliates (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	$ 1,582,075
Fair Value, Ending balance	1,610,775
Controlled Affiliated
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	63,919	$ 11,375
Gross Additions	975	55,834
Gross Reductions	(3,711)	(680)
Change in Unrealized Gains/ (Losses)	(3,851)	(5,970)
Fair Value, Ending balance	57,332	60,559
Dividend, Interest, PIK and Other Income	5,896	6,032
Controlled Affiliated | Envocore LLC
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	10,375	11,375
Gross Additions	974	235
Gross Reductions	(34)	(34)
Change in Unrealized Gains/ (Losses)	(1,429)	(99)
Fair Value, Ending balance	9,886	11,477
Dividend, Interest, PIK and Other Income	297	512
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	(2,240)
Change in Unrealized Gains/ (Losses)	(2,875)	(6,620)
Fair Value, Ending balance	33,889	38,148
Dividend, Interest, PIK and Other Income	5,280	5,520
Controlled Affiliated | Loadmaster Derrick & Equipment, Inc.
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	6,287
Gross Additions		1,807
Change in Unrealized Gains/ (Losses)	1,713	18
Fair Value, Ending balance	8,000	1,825
Dividend, Interest, PIK and Other Income	318
Controlled Affiliated | OEM Group, LLC
Investments In And Advances To Affiliates [Line Items]
Fair Value, Beginning balance	8,253
Gross Additions	1	9,024
Gross Reductions	(1,437)	(646)
Change in Unrealized Gains/ (Losses)	(1,260)	731
Fair Value, Ending balance	5,557	$ 9,109
Dividend, Interest, PIK and Other Income	$ 1