COMMITMENTS AND CONTINGENCIES - Unused Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Mar. 31, 2022
Other Commitments [Line Items]
Total unused commitments to extend financing	$ 159,740	$ 134,251
Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	87,197	57,640
Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	67,206	71,274
Other
Other Commitments [Line Items]
Total unused commitments to extend financing	5,337	5,337
Investment, Identifier [Axis]: ATS Operating, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	1,500
Investment, Identifier [Axis]: Acacia BuyerCo V LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	10,000	0
Investment, Identifier [Axis]: Acacia BuyerCo V LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,000	0
Investment, Identifier [Axis]: Acceleration, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	5,000	0
Investment, Identifier [Axis]: Acceleration, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	5,000	0
Investment, Identifier [Axis]: Air Conditioning Specialist, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,000	1,000
Investment, Identifier [Axis]: American Teleconferencing Services, Ltd. (DBA Premiere Global Services, Inc.), Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	148	117
Investment, Identifier [Axis]: ArborWorks, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,000	3,000
Investment, Identifier [Axis]: Cadmium, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	308
Investment, Identifier [Axis]: Catbird NYC, LLC, Other
Other Commitments [Line Items]
Total unused commitments to extend financing	125	125
Investment, Identifier [Axis]: Catbird NYC, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,000	4,000
Investment, Identifier [Axis]: Central Medical Supply LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,400	1,400
Investment, Identifier [Axis]: Central Medical Supply LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,200	1,200
Investment, Identifier [Axis]: CityVet Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	7,000
Investment, Identifier [Axis]: Dynamic Communities, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	500
Investment, Identifier [Axis]: Exact Borrower, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	0
Investment, Identifier [Axis]: Exact Borrower, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	0
Investment, Identifier [Axis]: FM Sylvan, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	10,000	0
Investment, Identifier [Axis]: Fast Sandwich, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	3,100
Investment, Identifier [Axis]: Flip Electronics, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	2,818
Investment, Identifier [Axis]: FoodPharma Subsidiary Holdings, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	5,470
Investment, Identifier [Axis]: GS Operating, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	3,205
Investment, Identifier [Axis]: GS Operating, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	1,540
Investment, Identifier [Axis]: Gains Intermediate, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	17,000	0
Investment, Identifier [Axis]: Gains Intermediate, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	0
Investment, Identifier [Axis]: GrammaTech, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	2,500
Investment, Identifier [Axis]: Gulf Pacific Acquisition, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,515	0
Investment, Identifier [Axis]: Gulf Pacific Acquisition, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	757	0
Investment, Identifier [Axis]: I-45 SLF LLC, Other
Other Commitments [Line Items]
Total unused commitments to extend financing	4,800	4,800
Investment, Identifier [Axis]: ISI Enterprises, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,200	1,200
Investment, Identifier [Axis]: ITA Holdings Group, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	1,250
Investment, Identifier [Axis]: Infolinks Media Buyco, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,250	2,250
Investment, Identifier [Axis]: Infolinks Media Buyco, LLC, Other
Other Commitments [Line Items]
Total unused commitments to extend financing	412	412
Investment, Identifier [Axis]: KMS, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,286	4,571
Investment, Identifier [Axis]: Klein Hersh, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	938
Investment, Identifier [Axis]: Lash OpCo, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	2,846
Investment, Identifier [Axis]: Lash OpCo, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	247	481
Investment, Identifier [Axis]: Lighting Retrofit International, LLC (DBA Envocore), Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,083	2,083
Investment, Identifier [Axis]: Lightning Intermediate II, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,852	0
Investment, Identifier [Axis]: Mako Steel LP, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	283	943
Investment, Identifier [Axis]: Microbe Formulas LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,627	0
Investment, Identifier [Axis]: Muenster Milling Company, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	6,000
Investment, Identifier [Axis]: Muenster Milling Company, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	7,000	5,000
Investment, Identifier [Axis]: NWN Parent Holdings, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	90	1,380
Investment, Identifier [Axis]: NeuroPsychiatric Hospitals, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	10,000
Investment, Identifier [Axis]: NeuroPsychiatric Hospitals, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	600	600
Investment, Identifier [Axis]: New Skinny Mixes, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	3,000	0
Investment, Identifier [Axis]: New Skinny Mixes, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,000	0
Investment, Identifier [Axis]: NinjaTrader, Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,692	4,692
Investment, Identifier [Axis]: NinjaTrader, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	2,500
Investment, Identifier [Axis]: Opco Borrower, LLC (DBA Giving Home Health Care), Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	667	0
Investment, Identifier [Axis]: Outerbox, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,000	0
Investment, Identifier [Axis]: Pipeline Technique Ltd., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	3,333	0
Investment, Identifier [Axis]: RTIC Subsidiary Holdings LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	822	0
Investment, Identifier [Axis]: Roof OpCo, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	4,644
Investment, Identifier [Axis]: Roof OpCo, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,833	3,056
Investment, Identifier [Axis]: Roseland Management, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,425	1,425
Investment, Identifier [Axis]: SIB Holdings, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	1,871
Investment, Identifier [Axis]: SIB Holdings, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	205	655
Investment, Identifier [Axis]: STATinMED, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	119	0
Investment, Identifier [Axis]: Shearwater Research, Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	3,262
Investment, Identifier [Axis]: Shearwater Research, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,446	2,446
Investment, Identifier [Axis]: South Coast Terminals LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,935	1,935
Investment, Identifier [Axis]: Spotlight AR, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,000	2,000
Investment, Identifier [Axis]: Student Resource Center, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	1,333
Investment, Identifier [Axis]: Systec Corporation (DBA Inspire Automation), Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	3,000	3,000
Investment, Identifier [Axis]: Systec Corporation (DBA Inspire Automation), Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,500	1,150
Investment, Identifier [Axis]: US CourtScript Holdings, Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	5,000	0
Investment, Identifier [Axis]: Versicare Management LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	5,000	0
Investment, Identifier [Axis]: Versicare Management LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	2,500	0
Investment, Identifier [Axis]: Wall Street Prep, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	1,000	1,000
Investment, Identifier [Axis]: Well-Foam, Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,500	4,500
Investment, Identifier [Axis]: Winter Services Operations, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,444	4,444
Investment, Identifier [Axis]: Winter Services Operations, LLC, Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	4,444	2,000
Investment, Identifier [Axis]: Zenfolio Inc., Revolving Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	0	1,000
Investment, Identifier [Axis]: Zips Car Wash, LLC - B, Delayed Draw Term Loans
Other Commitments [Line Items]
Total unused commitments to extend financing	$ 0	$ 3,801