FAIR VALUE MEASUREMENTS - Measurement Inputs and Valuation Techniques (Details) $ in Thousands	Sep. 30, 2022 USD ($)		Mar. 31, 2022 USD ($)
Fair Value
Total Investments	$ 1,056,931	[1],[2],[3]	$ 936,614	[4],[5],[6]
Significant Unobservable Inputs (Level 3)
Fair Value
Total Investments	1,006,034
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach
Fair Value
Total Investments	$ 803,645		$ 645,034
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.071		0.073
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Minimum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	5.6		5.5
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.627		0.306
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Maximum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	98		96.5
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.133		0.107
Significant Unobservable Inputs (Level 3) | First lien loans | Income Approach | Weighted Average | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	94.8		93.2
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach
Fair Value
Total Investments	$ 48,910		$ 94,838
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Investments, measurement input	97.6		80.2
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Minimum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			100.0
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Investments, measurement input	99.0		99.0
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Maximum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			102.0
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Investments, measurement input	98.2		98.1
Significant Unobservable Inputs (Level 3) | First lien loans | Market Approach | Weighted Average | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			101.8
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach
Fair Value
Total Investments	$ 36,264		$ 49,541
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.132		0.103
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Minimum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	88.7		97.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.300		0.378
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Maximum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	88.7		97.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.178		0.154
Significant Unobservable Inputs (Level 3) | Second lien loans | Income Approach | Weighted Average | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	88.7		97.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach
Fair Value
Total Investments	$ 14,173
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Investments, measurement input	91.2
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Minimum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Investments, measurement input	91.2
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Maximum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Investments, measurement input	91.2
Significant Unobservable Inputs (Level 3) | Second lien loans | Market Approach | Weighted Average | Exit Value
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach
Fair Value
Total Investments			$ 3,104
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.221
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input			8.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.221
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input			8.3
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.221
Significant Unobservable Inputs (Level 3) | Second lien loans | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input			8.3
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach
Fair Value
Total Investments			$ 650
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.274
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.274
Significant Unobservable Inputs (Level 3) | Subordinated debt | Income Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input			0.274
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach
Fair Value
Total Investments	$ 188		$ 172
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Investments, measurement input	1.000		100.0
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach
Fair Value
Total Investments	$ 271		$ 495
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.210		0.205
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	7.5		8.1
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.210		0.205
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	7.5		8.1
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.210		0.205
Significant Unobservable Inputs (Level 3) | Subordinated debt | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	7.5		8.1
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach
Fair Value
Total Investments	$ 750		$ 3,100
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0		100.0
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach
Fair Value
Total Investments	$ 52,020		$ 41,563
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.126		0.125
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	3.9		6.9
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.362		0.408
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	17.1		18.8
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.188		0.178
Significant Unobservable Inputs (Level 3) | Preferred equity | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	10.3		10.6
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Income Approach
Fair Value
Total Investments	$ 1,009		$ 2,090
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Income Approach | Minimum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	76.6		158.7
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Income Approach | Maximum | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	76.6		158.7
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Income Approach | Weighted Average | Third Party Broker Quote
Fair​ Value Measurement Input
Investments, measurement input	76.6		158.7
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach
Fair Value
Total Investments	$ 207		$ 1,757
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Minimum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Minimum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			351.4
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Maximum | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Maximum | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			351.4
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Weighted Average | Cost
Fair​ Value Measurement Input
Investments, measurement input	100.0
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Market Approach | Weighted Average | Exit Value
Fair​ Value Measurement Input
Investments, measurement input			351.4
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach
Fair Value
Total Investments	$ 48,597		$ 36,667
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.115		0.101
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Minimum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	5.4		4.2
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.362		0.322
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Maximum | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	13.0		11.4
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | Discount Rate
Fair​ Value Measurement Input
Investments, measurement input	0.168		0.181
Significant Unobservable Inputs (Level 3) | Common equity & warrants | Enterprise Value Waterfall Approach | Weighted Average | EBITDA Multiple
Fair​ Value Measurement Input
Investments, measurement input	10.1		8.5

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

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

[5] 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.

[6] 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.