BORROWINGS - Borrowings Outstanding (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Mar. 31, 2024
Debt Instrument [Line Items]
Outstanding Balance	$ 934,875		$ 934,875		$ 779,875
Unamortized Debt Issuance Costs and Debt Discount/Premium	(14,681)		(14,681)		(9,022)
Recorded Value	920,194		920,194		770,853
Estimated Fair Value	895,869		895,869		726,298
Line of Credit | Corporate Credit Facility
Debt Instrument [Line Items]
Recorded Value	190,000		190,000
SBA Debentures
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(4,279)		(4,279)		(4,305)
SBA Debentures | Unsecured Debt
Debt Instrument [Line Items]
Outstanding Balance	175,000		175,000		153,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(4,279)		(4,279)		(4,305)
Recorded Value	170,721		170,721		148,695
Estimated Fair Value	161,364		161,364		141,638
Corporate Credit Facility | Line of Credit
Debt Instrument [Line Items]
Outstanding Balance	190,000		190,000
Corporate Credit Facility | Line of Credit | Corporate Credit Facility
Debt Instrument [Line Items]
Outstanding Balance	190,000		190,000		265,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	0		0		0
Recorded Value	190,000		190,000		265,000
Estimated Fair Value	190,000		190,000		265,000
SPV Credit Facility | Line of Credit | SPV Credit Facility
Debt Instrument [Line Items]
Outstanding Balance	118,000		118,000		0
Unamortized Debt Issuance Costs and Debt Discount/Premium	0		0		0
Recorded Value	118,000		118,000		0
Estimated Fair Value	118,000		118,000		0
January 2026 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	0		0		(612)
January 2026 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance					140,000
Unamortized Debt Issuance Costs and Debt Discount/Premium					(612)
Recorded Value					139,388
Estimated Fair Value					118,249
Interest expense	1,208	$ 1,575	4,358	$ 4,725
October 2026 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,346)		(1,346)		(1,923)
October 2026 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	150,000		150,000		150,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,346)		(1,346)		(1,923)
Recorded Value	148,654		148,654		148,077
Estimated Fair Value	129,411		129,411		127,150
Interest expense	1,266	1,266	3,797	3,797
August 2028 Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,800)		(1,800)		(2,182)
August 2028 Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	71,875		71,875		71,875
Unamortized Debt Issuance Costs and Debt Discount/Premium	(1,800)		(1,800)		(2,182)
Recorded Value	70,075		70,075		69,693
Estimated Fair Value	74,118		74,118		74,261
Interest expense	1,393	1,393	4,178	3,033
2029 Convertible Notes
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Debt Discount/Premium	(7,256)		(7,256)		$ 0
2029 Convertible Notes | Notes
Debt Instrument [Line Items]
Outstanding Balance	230,000		230,000
2029 Convertible Notes | Convertible Debt
Debt Instrument [Line Items]
Outstanding Balance	230,000		230,000
Unamortized Debt Issuance Costs and Debt Discount/Premium	(7,256)		(7,256)
Recorded Value	222,744		222,744
Estimated Fair Value	222,976		222,976
Interest expense	$ 1,703	$ 0	$ 1,703	$ 0