CONVERTIBLE SENIOR NOTES AND CAPPED CALLS - Interest Expense (Details) - Convertible Debt - Aggregate Notes - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Contractual interest expense	$ 453	$ 453
Amortization of debt discount	4,332	4,068
Amortization of issuance costs	61	57
Total interest expense	$ 4,846	$ 4,578

Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration