BORROWINGS - Borrowings Outstanding (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Mar. 31, 2024
Debt Instrument [Line Items]
Outstanding Balance	$ 792,875	$ 779,875
Unamortized Debt Issuance Costs and Debt Discount/Premium	(7,844)	(9,022)
Recorded Value	785,031	770,853
Estimated Fair Value	757,032	726,298
Line of Credit | Corporate Credit Facility
Debt Instrument [Line Items]
Recorded Value	200,000
SBA Debentures
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(3,936)	(4,305)
SBA Debentures | Unsecured Debt
Debt Instrument [Line Items]
Outstanding Balance	153,000	153,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(3,936)	(4,305)
Recorded Value	149,064	148,695
Estimated Fair Value	148,977	141,638
Corporate Credit Facility | Line of Credit
Debt Instrument [Line Items]
Outstanding Balance	200,000
Corporate Credit Facility | Line of Credit | Corporate Credit Facility
Debt Instrument [Line Items]
Outstanding Balance	200,000	265,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	0	0
Recorded Value	200,000	265,000
Estimated Fair Value	200,000	265,000
SPV Credit Facility | Line of Credit | SPV Credit Facility
Debt Instrument [Line Items]
Outstanding Balance	78,000	0
Unamortized Debt Issuance Costs and Debt Discount/Premium	0	0
Recorded Value	78,000	0
Estimated Fair Value	78,000	0
January 2026 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(443)	(612)
January 2026 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	140,000	140,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(443)	(612)
Recorded Value	139,557	139,388
Estimated Fair Value	122,895	118,249
October 2026 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,538)	(1,923)
October 2026 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	150,000	150,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,538)	(1,923)
Recorded Value	148,462	148,077
Estimated Fair Value	132,784	127,150
August 2028 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,927)	(2,182)
August 2028 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	71,875	71,875
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,927)	(2,182)
Recorded Value	69,948	69,693
Estimated Fair Value	$ 74,376	$ 74,261