DEBT - INTEREST EXPENSE COMPONENTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 18, 2013
Debt Instrument [Line Items]
Non-cash amortization of discount on Convertible Notes	$ 91	$ 5,237	[1]
Amortization of debt issuance costs	$ 32	188	[1]
1.00% Convertible Notes due 2018
Debt Instrument [Line Items]
Interest rate	1.00%
Convertible Debt | 1.00% Convertible Notes due 2018
Debt Instrument [Line Items]
Interest rate				1.00%
Cash interest expense (coupon interest expense)	$ 1	448
Non-cash amortization of discount on Convertible Notes	91	5,237
Amortization of debt issuance costs	3	160
Total interest expense related to Convertible Notes	$ 95	$ 5,845

[1] Prior period amounts have been adjusted retrospectively to reflect the adoption of ASU 2016-08, Statement of Cash Flows (Topic 230): Restricted Cash. Refer to Note 1 for further discussion.