Investments - Investments By Industry (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Consolidated Schedule of Investments
Investments, amortized cost	$ 2,356,143	$ 2,311,384
Percentage of Total Portfolio	100.00%	100.00%
Investments at fair value	$ 2,293,522	$ 2,289,105
Percentage of Total Portfolio	100.00%	100.00%
Aerospace and Defense
Consolidated Schedule of Investments
Investments, amortized cost	$ 398,665	$ 309,458
Percentage of Total Portfolio	16.90%	13.40%
Investments at fair value	$ 380,118	$ 282,598
Percentage of Total Portfolio	16.60%	12.30%
Investment Vehicles
Consolidated Schedule of Investments
Investments, amortized cost	$ 284,780	$ 165,033
Percentage of Total Portfolio	11.90%	7.10%
Investments at fair value	$ 282,498	$ 169,881
Percentage of Total Portfolio	12.30%	7.40%
High Tech Industries
Consolidated Schedule of Investments
Investments, amortized cost	$ 220,512	$ 182,811
Percentage of Total Portfolio	9.40%	7.90%
Investments at fair value	$ 217,497	$ 183,069
Percentage of Total Portfolio	9.50%	8.00%
Services, Business
Consolidated Schedule of Investments
Investments, amortized cost	$ 170,902	$ 226,035
Percentage of Total Portfolio	7.30%	9.80%
Investments at fair value	$ 163,918	$ 225,437
Percentage of Total Portfolio	7.10%	9.80%
Consumer Sector, Non-Durable
Consolidated Schedule of Investments
Investments, amortized cost	$ 130,849	$ 179,733
Percentage of Total Portfolio	5.60%	7.80%
Investments at fair value	$ 129,695	$ 182,063
Percentage of Total Portfolio	5.70%	8.00%
Construction and Building
Consolidated Schedule of Investments
Investments, amortized cost	$ 117,017	$ 70,256
Percentage of Total Portfolio	5.00%	3.00%
Investments at fair value	$ 113,634	$ 68,570
Percentage of Total Portfolio	5.00%	3.00%
Healthcare and Pharmaceuticals
Consolidated Schedule of Investments
Investments, amortized cost	$ 101,715	$ 102,116
Percentage of Total Portfolio	4.30%	4.40%
Investments at fair value	$ 99,633	$ 100,771
Percentage of Total Portfolio	4.30%	4.40%
Transportation: Cargo
Consolidated Schedule of Investments
Investments, amortized cost	$ 86,852	$ 103,012
Percentage of Total Portfolio	3.70%	4.50%
Investments at fair value	$ 91,874	$ 106,458
Percentage of Total Portfolio	4.00%	4.70%
Automotive Sector
Consolidated Schedule of Investments
Investments, amortized cost	$ 78,189	$ 87,597
Percentage of Total Portfolio	3.30%	3.80%
Investments at fair value	$ 78,215	$ 88,555
Percentage of Total Portfolio	3.40%	3.90%
Transportation: Consumer
Consolidated Schedule of Investments
Investments, amortized cost	$ 81,733	$ 80,027
Percentage of Total Portfolio	3.50%	3.50%
Investments at fair value	$ 78,151	$ 69,040
Percentage of Total Portfolio	3.40%	3.00%
Energy: Oil and Gas
Consolidated Schedule of Investments
Investments, amortized cost	$ 57,002	$ 69,588
Percentage of Total Portfolio	2.40%	3.00%
Investments at fair value	$ 74,898	$ 79,548
Percentage of Total Portfolio	3.30%	3.50%
Consumer Goods: Durable
Consolidated Schedule of Investments
Investments, amortized cost	$ 84,266	$ 83,903
Percentage of Total Portfolio	3.60%	3.60%
Investments at fair value	$ 74,692	$ 76,575
Percentage of Total Portfolio	3.30%	3.30%
Fire Insurance
Consolidated Schedule of Investments
Investments, amortized cost	$ 64,944	$ 62,165
Percentage of Total Portfolio	2.80%	2.70%
Investments at fair value	$ 62,954	$ 63,123
Percentage of Total Portfolio	2.70%	2.80%
Retail Sector
Consolidated Schedule of Investments
Investments, amortized cost	$ 60,350	$ 83,036
Percentage of Total Portfolio	2.60%	3.60%
Investments at fair value	$ 53,266	$ 83,064
Percentage of Total Portfolio	2.30%	3.60%
Fire Finance
Consolidated Schedule of Investments
Investments, amortized cost	$ 49,741	$ 24,245
Percentage of Total Portfolio	2.10%	1.00%
Investments at fair value	$ 47,545	$ 24,452
Percentage of Total Portfolio	2.10%	1.10%
Telecommunications
Consolidated Schedule of Investments
Investments, amortized cost	$ 46,415	$ 40,938
Percentage of Total Portfolio	2.00%	1.80%
Investments at fair value	$ 47,204	$ 41,570
Percentage of Total Portfolio	2.10%	1.80%
Hotel, Gaming & Leisure
Consolidated Schedule of Investments
Investments, amortized cost	$ 37,159	$ 53,232
Percentage of Total Portfolio	1.60%	2.30%
Investments at fair value	$ 36,068	$ 51,956
Percentage of Total Portfolio	1.60%	2.30%
Environmental Industries
Consolidated Schedule of Investments
Investments, amortized cost	$ 35,140
Percentage of Total Portfolio	1.50%
Investments at fair value	$ 34,538
Percentage of Total Portfolio	1.50%
Media: Diversified and Production
Consolidated Schedule of Investments
Investments, amortized cost	$ 36,721	$ 46,420
Percentage of Total Portfolio	1.60%	2.00%
Investments at fair value	$ 34,136	$ 44,835
Percentage of Total Portfolio	1.50%	2.00%
Capital Equipment
Consolidated Schedule of Investments
Investments, amortized cost	$ 31,046	$ 65,129
Percentage of Total Portfolio	1.30%	2.80%
Investments at fair value	$ 30,728	$ 64,841
Percentage of Total Portfolio	1.30%	2.80%
Media: Advertising, Printing and Publishing
Consolidated Schedule of Investments
Investments, amortized cost	$ 54,169	$ 50,389
Percentage of Total Portfolio	2.30%	2.20%
Investments at fair value	$ 27,819	$ 39,459
Percentage of Total Portfolio	1.20%	1.70%
Wholesale
Consolidated Schedule of Investments
Investments, amortized cost	$ 26,426	$ 77,737
Percentage of Total Portfolio	1.10%	3.40%
Investments at fair value	$ 27,640	$ 80,070
Percentage of Total Portfolio	1.20%	3.50%
Media: Publishing
Consolidated Schedule of Investments
Investments, amortized cost	$ 21,507
Percentage of Total Portfolio	0.90%
Investments at fair value	$ 20,356
Percentage of Total Portfolio	0.90%
Services, Consumer [Business]
Consolidated Schedule of Investments
Investments, amortized cost	$ 17,585	$ 40,467
Percentage of Total Portfolio	0.70%	1.80%
Investments at fair value	$ 17,823	$ 41,236
Percentage of Total Portfolio	0.80%	1.80%
Containers, Packaging and Glass
Consolidated Schedule of Investments
Investments, amortized cost	$ 16,372	$ 27,379
Percentage of Total Portfolio	0.70%	1.20%
Investments at fair value	$ 16,071	$ 27,378
Percentage of Total Portfolio	0.70%	1.20%
Beverage, Food and Tobacco
Consolidated Schedule of Investments
Investments, amortized cost	$ 7,359	$ 7,563
Percentage of Total Portfolio	0.30%	0.30%
Investments at fair value	$ 14,702	$ 19,755
Percentage of Total Portfolio	0.60%	0.90%
Chemicals, Plastics & Rubber
Consolidated Schedule of Investments
Investments, amortized cost	$ 14,177	$ 26,135
Percentage of Total Portfolio	0.60%	1.10%
Investments at fair value	$ 14,065	$ 26,863
Percentage of Total Portfolio	0.60%	1.20%
Banking
Consolidated Schedule of Investments
Investments, amortized cost	$ 7,736	$ 18,370
Percentage of Total Portfolio	0.30%	0.80%
Investments at fair value	$ 7,980	$ 18,690
Percentage of Total Portfolio	0.30%	0.80%
Consumer goods: Wholesale
Consolidated Schedule of Investments
Investments, amortized cost	$ 8,839	$ 14,870
Percentage of Total Portfolio	0.40%	0.60%
Investments at fair value	$ 7,086	$ 14,827
Percentage of Total Portfolio	0.30%	0.60%
Hospitality Holdings
Consolidated Schedule of Investments
Investments, amortized cost	$ 5,000	$ 5,000
Percentage of Total Portfolio	0.20%	0.20%
Investments at fair value	$ 5,841	$ 5,442
Percentage of Total Portfolio	0.30%	0.20%
Media: Broadcasting and Subscription
Consolidated Schedule of Investments
Investments, amortized cost	$ 2,825	$ 8,740
Percentage of Total Portfolio	0.10%	0.40%
Investments at fair value	$ 2,717	$ 8,979
Percentage of Total Portfolio	0.10%	0.40%
Banking, Finance, Insurance and Real Estate
Consolidated Schedule of Investments
Investments, amortized cost	$ 150
Percentage of Total Portfolio	0.00%
Investments at fair value	$ 160
Percentage of Total Portfolio	0.00%