CONVERTIBLE SENIOR NOTES AND CAPPED CALL - Interest Expense (Details) - Convertible Debt - Convertible Senior Notes - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Sep. 30, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 360	$ 719
Amortization of debt discount	3,198	6,344
Amortization of issuance costs	27	53
Total interest expense	$ 3,585	$ 7,116

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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

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