FAIR VALUE MEASUREMENTS - Measurement Inputs and Valuation Techniques (Details) $ in Thousands	Dec. 31, 2023 USD ($)		Mar. 31, 2023 USD ($)
Fair Value
Investments at fair value	$ 1,365,037	[1],[2],[3],[4],[5],[6],[7]	$ 1,206,388	[8],[9],[10]
Significant Unobservable Inputs (Level 3)
Fair Value
Investments at fair value	1,310,837
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach
Fair Value
Investments at fair value	$ 1,096,012		$ 953,918
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.064		0.069
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	98.9		5.1
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.536		0.262
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	98.9		96.5
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.138		0.130
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	98.9		93.9
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach
Fair Value
Investments at fair value	$ 50,343		$ 41,923
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	97.5		94.1
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		98.1
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	98.1		97.9
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach
Fair Value
Investments at fair value			$ 5,143
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | First lien loans | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach
Fair Value
Investments at fair value	$ 34,614		$ 32,226
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.129		0.183
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Minimum | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	35.0		61.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.204		0.343
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Maximum | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	35.0		61.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.167		0.251
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Weighted Average | Third Party Broker Quote
Fair​ Value Measurement Input
Significant Level 3 Inputs	35.0		61.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach
Fair Value
Investments at fair value			$ 3,594
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs			0.272
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs			9.4
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach
Fair Value
Investments at fair value	$ 210		$ 205
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	1.000		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach
Fair Value
Investments at fair value	$ 558		$ 586
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.133		0.202
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	5.9		6.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.251		0.250
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	8.0		7.7
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.170		0.218
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	6.6		6.6
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach
Fair Value
Investments at fair value	$ 2,833		$ 3,875
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach
Fair Value
Investments at fair value	$ 65,811		$ 59,518
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.087		0.117
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	4.1		4.7
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.291		0.308
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	16.8		16.7
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.171		0.171
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	9.6		9.8
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach
Fair Value
Investments at fair value	$ 1,167		$ 1,080
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Minimum | Exit Value
Fair​ Value Measurement Input
Significant Level 3 Inputs			100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Maximum | Exit Value
Fair​ Value Measurement Input
Significant Level 3 Inputs			100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Significant Level 3 Inputs	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Weighted Average | Exit Value
Fair​ Value Measurement Input
Significant Level 3 Inputs			100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach
Fair Value
Investments at fair value	$ 59,289		$ 53,064
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.087		0.114
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	4.1		5.5
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.266		0.366
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	16.5		18.6
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Significant Level 3 Inputs	0.165		0.182
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Significant Level 3 Inputs	9.0		9.5

[1] All portfolio company headquarters are based in the United States, unless otherwise noted.

[2] 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.

[3] Non-Control/Non-Affiliate investments are generally defined by the 1940 Act, as investments that are neither control investments nor affiliate investments. At December 31, 2023, the Company held $1,124.9 million of non-control/non-affiliate investments, which represented approximately 82.4% of the Company’s investment assets. The fair value of these investments as a percent of net assets is 156.0%.

[4] Affiliate investments are generally defined by the 1940 Act as investments in which between 5% and 25% of the voting securities are owned and the investments are not classified as control investments. At December 31, 2023, the Company held $186.0 million of affiliate investments, which represented approximately 13.6% of the Company’s investment assets. The fair value of these investments as a percent of net assets is 25.8%.

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

[6] Control investments are generally defined by the 1940 Act as investments in which more than 25% of the voting securities are owned. At December 31, 2023, the Company held $54.2 million of control investments, which represented approximately 4.0% of the Company’s investment assets were . The fair value of these investments as a percent of net assets is 7.5%.

[7] 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 valuation committee comprised of certain officers of the Company (the "Valuation Committee") as the valuation designee of the Board of Directors (the "Valuation Designee") pursuant to Rule 2a-5 under the Investment Company Act of 1940, as amended (the “1940 Act”), using significant unobservable Level 3 inputs. Refer to Note 4 - Fair Value Measurements for further discussion.

[8] 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.

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

[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 - Fair Value Measurements to our audited consolidated financial statements for further discussion.