SIGNIFICANT SUBSIDIARIES - Summarized Financial Information Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2023		Mar. 31, 2022		Mar. 31, 2021	Mar. 31, 2020
Investment Company, Nonconsolidated Subsidiary [Line Items]
Cost	$ 1,220,152	[1],[2],[3],[4]	$ 938,303	[5],[6],[7],[8]
Total Investments	1,206,388	[1],[3],[9]	936,614	[5],[7],[10]
Cash and cash equivalents	21,585		11,431
Deferred financing costs and other assets	3,717		4,038
Total assets	1,257,684		973,957
Credit facility	235,000		205,000
Other liabilities	16,761		14,808
Total liabilities	667,276		553,090
Total net assets	590,408		420,867		$ 336,251	$ 272,222
Total liabilities and net assets	1,257,684		973,957
I-45 SLF LLC
Investment Company, Nonconsolidated Subsidiary [Line Items]
Cost	169,874		187,714
Total Investments	143,712		176,704
Cash and cash equivalents	6,478		9,949
Interest receivable	1,145		850
Accounts receivable	1,038		123
Deferred financing costs and other assets	416		1,518
Total assets	152,789		189,144
Credit facility	86,000		114,500
Other liabilities	2,674		2,596
Total liabilities	88,674		117,096
Total net assets	64,115		72,048
Total liabilities and net assets	$ 152,789		$ 189,144

[1] All debt investments are income-producing, unless otherwise noted. Equity investments are non-income producing, unless otherwise noted.

[2] As of March 31, 2023, the cumulative gross unrealized appreciation for U.S. federal income tax purposes was approximately $72.3 million; cumulative gross unrealized depreciation for federal income tax purposes was $76.8 million. Cumulative net unrealized depreciation was $4.5 million, based on a tax cost of $1,210.8 million.

[3] Equity ownership may be held in shares or units of a company that is either wholly owned by the portfolio company or under common control by the same parent company to the portfolio company.

[4] Negative cost in this column represents the original issue discount of certain undrawn revolvers and delayed draw term loans.

[5] All debt investments are income-producing, unless otherwise noted. Equity investments and warrants are non-income producing, unless otherwise noted.

[6] As of March 31, 2022, the cumulative gross unrealized appreciation for U.S. federal income tax purposes is approximately $67.8 million; cumulative gross unrealized depreciation for federal income tax purposes is $61.7 million. Cumulative net unrealized appreciation is $6.1 million, based on a tax cost of $852.4 million.

[7] Equity ownership may be held in shares or units of a company that is either wholly owned by the portfolio company or under common control by the same parent company to the portfolio company.

[8] Represents amortized cost. Negative cost in this column represents the original issue discount of certain undrawn revolvers and delayed draw term loans.

[9] The Company's investment portfolio is comprised entirely of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not readily available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the Board of Directors, using significant unobservable Level 3 inputs. Refer to Note 4 - Fair Value Measurements for further discussion.

[10] The Company's investment portfolio is comprised entirely of debt and equity securities of privately held companies for which quoted prices falling within the categories of Level 1 and Level 2 inputs are not readily available. Therefore, the Company values all of its portfolio investments at fair value, as determined in good faith by the Board of Directors, using significant unobservable Level 3 inputs. Refer to Note 4 for further discussion.