Investments - Composition of the Company's investment portfolio by geographic region, at amortized cost and fair value (with corresponding percentage of total portfolio investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023		Dec. 31, 2022
Investments
Amortized cost	$ 2,523,064	[1]	$ 1,465,352	[2]
Total investments	$ 2,528,167	[1],[3]	$ 1,468,996	[2],[4]
Concentration risk, percentage	100.00%		100.00%
International
Investments
Amortized cost	$ 116,117		$ 62,244
Total investments	$ 112,077		$ 59,706
International | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	4.60%		4.30%
International | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	4.40%		4.10%
Midwest
Investments
Amortized cost	$ 464,411		$ 312,637
Total investments	$ 462,371		$ 313,240
Midwest | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	18.40%		21.30%
Midwest | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	18.30%		21.30%
Northeast
Investments
Amortized cost	$ 602,303		$ 245,445
Total investments	$ 605,226		$ 244,305
Northeast | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	23.90%		16.70%
Northeast | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	23.90%		16.60%
Northwest
Investments
Amortized cost	$ 72,401		$ 66,839
Total investments	$ 73,706		$ 67,226
Northwest | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	2.90%		4.60%
Northwest | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	2.90%		4.60%
Southeast
Investments
Amortized cost	$ 609,720		$ 353,079
Total investments	$ 616,182		$ 360,465
Southeast | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	24.20%		24.10%
Southeast | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	24.40%		24.50%
Southwest
Investments
Amortized cost	$ 303,643		$ 183,722
Total investments	$ 303,605		$ 181,981
Southwest | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	12.00%		12.50%
Southwest | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	12.00%		12.40%
West
Investments
Amortized cost	$ 354,469		$ 241,386
Total investments	$ 355,000		$ 242,073
West | Investment Owned, At Cost | Geographic Concentration Risk
Investments
Concentration risk, percentage	14.00%		16.50%
West | Investment Owned, At Fair Value | Geographic Concentration Risk
Investments
Concentration risk, percentage	14.10%		16.50%

[1] All of the Company's investments are issued by eligible portfolio companies, as defined in the Investment Company Act of 1940, as amended, (the “1940 Act”), unless otherwise noted. All of the Company's investments are issued by U.S. portfolio companies unless otherwise noted.

[2] All of the Company's investments are issued by eligible portfolio companies, as defined in the Investment Company Act of 1940, as amended, (the “1940 Act”), unless otherwise noted. All of the Company's investments are issued by U.S. portfolio companies unless otherwise noted.

[3] Except as otherwise noted, because there is no readily available market value for these investments, the fair value of each of these investments is determined in good faith using significant unobservable inputs by the Valuation Designee. (See Note 4 in the accompanying notes to the consolidated financial statements.)

[4] Except as otherwise noted, because there is no readily available market value for these investments, the fair value of each of these investments is determined in good faith using significant unobservable inputs by the Valuation Designee. (See Note 4 in the accompanying notes to the consolidated financial statements.)