INVESTMENTS - Industry Composition (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024		Dec. 31, 2023
Schedule of Investments [Line Items]
Total investments at fair value	$ 1,363,048		$ 1,349,121
Percentage of Total Net Assets	203.40%	[1]	206.90%	[2]
Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 143,697		$ 146,477
Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	100.00%		100.00%
Percentage of Total Net Assets	203.40%		206.90%
Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	100.00%		100.00%
Aerospace and Defense
Schedule of Investments [Line Items]
Total investments at fair value	$ 84,035		$ 81,217
Percentage of Total Net Assets			12.50%
Aerospace and Defense | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 15,105		$ 15,125
Aerospace and Defense | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	6.20%		6.00%
Percentage of Total Net Assets	12.50%		12.50%
Aerospace and Defense | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	10.50%		10.30%
Automotive
Schedule of Investments [Line Items]
Total investments at fair value	$ 18,403		$ 16,830
Percentage of Total Net Assets			2.60%
Automotive | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.30%		1.20%
Percentage of Total Net Assets	2.80%		2.60%
Banking, Finance, Insurance and Real Estate
Schedule of Investments [Line Items]
Total investments at fair value	$ 224,287		$ 227,415
Percentage of Total Net Assets			34.90%
Banking, Finance, Insurance and Real Estate | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 16,190		$ 16,325
Banking, Finance, Insurance and Real Estate | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	16.50%		16.90%
Percentage of Total Net Assets	33.50%		34.90%
Banking, Finance, Insurance and Real Estate | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	11.30%		11.20%
Beverage, Food and Tobacco
Schedule of Investments [Line Items]
Total investments at fair value	$ 33,057		$ 24,197
Percentage of Total Net Assets			3.70%
Beverage, Food and Tobacco | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 7,577		$ 7,531
Beverage, Food and Tobacco | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.40%		1.80%
Percentage of Total Net Assets	4.90%		3.70%
Beverage, Food and Tobacco | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	5.30%		5.10%
Capital Equipment
Schedule of Investments [Line Items]
Total investments at fair value	$ 46,833		$ 46,500
Percentage of Total Net Assets			7.10%
Capital Equipment | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	3.40%		3.50%
Percentage of Total Net Assets	7.00%		7.10%
Chemicals, Plastics, and Rubber
Schedule of Investments [Line Items]
Total investments at fair value	$ 29,105		$ 25,679
Percentage of Total Net Assets			3.90%
Chemicals, Plastics, and Rubber | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 1,937		$ 1,269
Chemicals, Plastics, and Rubber | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.10%		1.90%
Percentage of Total Net Assets	4.40%		3.90%
Chemicals, Plastics, and Rubber | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.30%		0.90%
Construction and Building
Schedule of Investments [Line Items]
Total investments at fair value	$ 10,719		$ 10,070
Percentage of Total Net Assets			1.60%
Construction and Building | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 1,450		$ 1,364
Construction and Building | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.80%		0.70%
Percentage of Total Net Assets	1.60%		1.60%
Construction and Building | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.00%		0.90%
Consumer Goods: Durable
Schedule of Investments [Line Items]
Total investments at fair value	$ 25,526		$ 25,563
Percentage of Total Net Assets			3.90%
Consumer Goods: Durable | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 1,731		$ 1,725
Consumer Goods: Durable | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.90%		1.90%
Percentage of Total Net Assets	3.80%		3.90%
Consumer Goods: Durable | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.20%		1.20%
Consumer Goods: Non-durable
Schedule of Investments [Line Items]
Total investments at fair value	$ 14,343		$ 9,987
Percentage of Total Net Assets			1.50%
Consumer Goods: Non-durable | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 6,026		$ 6,205
Consumer Goods: Non-durable | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.10%		0.70%
Percentage of Total Net Assets	2.10%		1.50%
Consumer Goods: Non-durable | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	4.20%		4.20%
Containers, Packaging and Glass
Schedule of Investments [Line Items]
Total investments at fair value	$ 22,927		$ 23,032
Percentage of Total Net Assets			3.50%
Containers, Packaging and Glass | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 6,459		$ 6,607
Containers, Packaging and Glass | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.70%		1.70%
Percentage of Total Net Assets	3.40%		3.50%
Containers, Packaging and Glass | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	4.50%		4.50%
Energy: Electricity
Schedule of Investments [Line Items]
Total investments at fair value	$ 6,297		$ 6,676
Percentage of Total Net Assets			1.00%
Energy: Electricity | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.50%		0.50%
Percentage of Total Net Assets	1.00%		1.00%
Energy: Oil and Gas
Schedule of Investments [Line Items]
Total investments at fair value	$ 2,669		$ 2,670
Percentage of Total Net Assets			0.40%
Energy: Oil and Gas | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.20%		0.20%
Percentage of Total Net Assets	0.40%		0.40%
Environmental Industries
Schedule of Investments [Line Items]
Total investments at fair value	$ 29,225		$ 30,266
Percentage of Total Net Assets			4.70%
Environmental Industries | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.10%		2.20%
Percentage of Total Net Assets	4.40%		4.70%
Healthcare and Pharmaceuticals
Schedule of Investments [Line Items]
Total investments at fair value	$ 124,015		$ 130,845
Percentage of Total Net Assets			20.10%
Healthcare and Pharmaceuticals | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 16,635		$ 17,205
Healthcare and Pharmaceuticals | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	9.10%		9.70%
Percentage of Total Net Assets	18.50%		20.10%
Healthcare and Pharmaceuticals | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	11.60%		11.80%
High Tech Industries
Schedule of Investments [Line Items]
Total investments at fair value	$ 137,613		$ 141,704
Percentage of Total Net Assets			21.70%
High Tech Industries | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 20,898		$ 20,942
High Tech Industries | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	10.10%		10.50%
Percentage of Total Net Assets	20.50%		21.70%
High Tech Industries | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	14.50%		14.30%
Hotel, Gaming and Leisure
Schedule of Investments [Line Items]
Total investments at fair value	$ 21,572		$ 19,595
Percentage of Total Net Assets			3.00%
Hotel, Gaming and Leisure | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.60%		1.50%
Percentage of Total Net Assets	3.20%		3.00%
Investment Funds and Vehicles
Schedule of Investments [Line Items]
Total investments at fair value	$ 36,725		$ 37,212
Percentage of Total Net Assets			5.70%
Investment Funds and Vehicles | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.70%		2.80%
Percentage of Total Net Assets	5.50%		5.70%
Media: Advertising, Printing and Publishing
Schedule of Investments [Line Items]
Total investments at fair value	$ 32,578		$ 32,570
Percentage of Total Net Assets			5.00%
Media: Advertising, Printing and Publishing | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 1,955		$ 1,957
Media: Advertising, Printing and Publishing | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.40%		2.40%
Percentage of Total Net Assets	4.90%		5.00%
Media: Advertising, Printing and Publishing | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.40%		1.30%
Media: Broadcasting and Subscription
Schedule of Investments [Line Items]
Total investments at fair value	$ 8,706		$ 8,867
Percentage of Total Net Assets			1.40%
Media: Broadcasting and Subscription | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.60%		0.70%
Percentage of Total Net Assets	1.30%		1.40%
Media: Diversified and Production
Schedule of Investments [Line Items]
Total investments at fair value	$ 46,497		$ 45,924
Percentage of Total Net Assets			7.10%
Media: Diversified and Production | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 4,274		$ 4,306
Media: Diversified and Production | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	3.40%		3.40%
Percentage of Total Net Assets	6.90%		7.10%
Media: Diversified and Production | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	3.00%		2.90%
Services: Business
Schedule of Investments [Line Items]
Total investments at fair value	$ 216,121		$ 201,007
Percentage of Total Net Assets			30.80%
Services: Business | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 21,536		$ 21,900
Services: Business | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	15.90%		14.90%
Percentage of Total Net Assets	32.30%		30.80%
Services: Business | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	15.00%		15.00%
Services: Consumer
Schedule of Investments [Line Items]
Total investments at fair value	$ 69,268		$ 69,643
Percentage of Total Net Assets			10.70%
Services: Consumer | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 12,291		$ 12,509
Services: Consumer | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	5.10%		5.20%
Percentage of Total Net Assets	10.30%		10.70%
Services: Consumer | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	8.50%		8.50%
Structured Products
Schedule of Investments [Line Items]
Total investments at fair value	$ 33,667		$ 32,763
Percentage of Total Net Assets			5.00%
Structured Products | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.50%		2.40%
Percentage of Total Net Assets	5.00%		5.00%
Telecommunications
Schedule of Investments [Line Items]
Total investments at fair value	$ 18,276		$ 18,341
Percentage of Total Net Assets			2.80%
Telecommunications | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 3,213		$ 3,243
Telecommunications | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	1.30%		1.40%
Percentage of Total Net Assets	2.70%		2.80%
Telecommunications | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	2.20%		2.20%
Transportation: Cargo
Schedule of Investments [Line Items]
Total investments at fair value	$ 58,929		$ 68,703
Percentage of Total Net Assets			10.50%
Transportation: Cargo | Banff Partners LP
Schedule of Investments [Line Items]
Total investments at fair value	$ 6,420		$ 8,264
Transportation: Cargo | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	4.30%		5.10%
Percentage of Total Net Assets	8.80%		10.50%
Transportation: Cargo | Investment Owned, At Fair Value | Industry Concentration Risk | Banff Partners LP
Schedule of Investments [Line Items]
Percentage of Total Portfolio	4.50%		5.70%
Transportation: Consumer
Schedule of Investments [Line Items]
Total investments at fair value	$ 2,000		$ 1,900
Percentage of Total Net Assets			0.30%
Transportation: Consumer | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.10%		0.10%
Percentage of Total Net Assets	0.30%		0.30%
Utilities: Electric
Schedule of Investments [Line Items]
Total investments at fair value	$ 9,655		$ 9,945
Percentage of Total Net Assets			1.50%
Utilities: Electric | Investment Owned, At Fair Value | Industry Concentration Risk
Schedule of Investments [Line Items]
Percentage of Total Portfolio	0.70%		0.70%
Percentage of Total Net Assets	1.40%		1.50%

[1] Fair value as a percentage of net assets.

[2] Fair value as a percentage of net assets.