FAIR VALUE MEASUREMENTS - Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($) $ in Thousands	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
First lien loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 1,309,449	$ 1,000,984
Realized & Unrealized Gains (Losses)	(14,912)	(5,395)
Purchases of Investments	196,254	200,986
Repayments	(128,801)	(40,307)
PIK Interest Capitalized	5,984	2,678
Divestitures	(22,585)	(13,875)
Conversion/Exchange of Security3	0	(3,791)
Fair value. ending balance	1,345,389	1,141,280
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(15,970)	(5,740)
Second lien loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	33,774	35,820
Realized & Unrealized Gains (Losses)	(1,986)	2,184
Purchases of Investments	(4)	126
Repayments	(3,420)	(1,114)
PIK Interest Capitalized	70	18
Divestitures	0	0
Conversion/Exchange of Security3	(1,062)	0
Fair value. ending balance	27,372	37,034
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(106)	2,181
Subordinated debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	1,336	791
Realized & Unrealized Gains (Losses)	29	(28)
Purchases of Investments	57	0
Repayments	0	(20)
PIK Interest Capitalized	11	17
Divestitures	0	0
Conversion/Exchange of Security3	(153)	0
Fair value. ending balance	1,280	760
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	21	(28)
Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	71,127	63,393
Realized & Unrealized Gains (Losses)	(132)	(1,345)
Purchases of Investments	3,557	4,392
Repayments	0	0
PIK Interest Capitalized	0	0
Divestitures	0	0
Conversion/Exchange of Security3	0	0
Fair value. ending balance	74,552	66,440
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(132)	(1,345)
Common equity & warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	60,875	54,144
Realized & Unrealized Gains (Losses)	(5,861)	(3,030)
Purchases of Investments	3,685	3,127
Repayments	0	0
PIK Interest Capitalized	0	0
Divestitures	0	(3,402)
Conversion/Exchange of Security3	1,215	3,791
Fair value. ending balance	59,914	54,630
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(5,062)	(3,217)
Total Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	1,476,561	1,155,132
Realized & Unrealized Gains (Losses)	(22,862)	(7,614)
Purchases of Investments	203,549	208,631
Repayments	(132,221)	(41,441)
PIK Interest Capitalized	6,065	2,713
Divestitures	(22,585)	(17,277)
Conversion/Exchange of Security3	0	0
Fair value. ending balance	1,508,507	1,300,144
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(21,249)	$ (8,149)
Cost basis allocated from first lien debt to warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Conversion/Exchange of Security3	$ 3,800