CONVERTIBLE SENIOR NOTES AND CAPPED CALL - Carrying Amount of the Liability Component (Details) - Convertible Debt - Aggregate Notes - USD ($)	Dec. 31, 2020	Mar. 31, 2020	Dec. 01, 2019
Debt Instrument [Line Items]
Principal	$ 362,500,000	$ 362,500,000	$ 362,500,000
Unamortized debt discount	(57,587,000)	(69,987,000)
Unamortized issuance costs	(802,000)	(976,000)
Net carrying amount	$ 304,111,000	$ 291,537,000