DEBT - INTEREST EXPENSE COMPONENTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019		Mar. 31, 2018		Jun. 18, 2013
Debt Instrument [Line Items]
Non-cash amortization of discount on Convertible Notes	$ 0	$ 91	[1]	$ 15,662	[1]
1.00% Convertible Notes due 2018
Debt Instrument [Line Items]
Interest rate		1.00%		1.00%
Convertible Debt | 1.00% Convertible Notes due 2018
Debt Instrument [Line Items]
Interest rate						1.00%
Cash interest expense (coupon interest expense)	0	$ 1		$ 539
Non-cash amortization of discount on Convertible Notes	0	91		15,662
Amortization of debt issuance costs	0	3		466
Total interest expense related to Convertible Notes	$ 0	$ 95		$ 16,667

[1] Prior period amounts have been adjusted retrospectively to reflect the adoption of ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. Refer to Note 1 for further discussion.