STOCK-BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021
Number of Shares
Outstanding, beginning balance (in shares)	1,813
Granted (in shares)	0
Exercised (in shares)	(640)
Cancelled/Forfeited (in shares)	(18)
Outstanding, ending balance (in shares)		1,813
Vested and expected to vest at June 30, 2021 (in shares)	1,155
Exercisable at June 30, 2021 (in shares)	1,136
Weighted Average Exercise Price Per Share
Outstanding, beginning balance (in dollars per share)	$ 9.46
Granted (in dollars per share)	0
Exercised (in dollars per share)	8.60
Cancelled/Forfeited (in dollars per share)	21.94
Outstanding, ending balance (in dollars per share)	9.74	$ 9.46
Vested and expected to vest, ending balance (in dollars per share)	9.73
Exercisable, end of period (in dollars per share)	$ 9.57
Weighted Average Remaining Contractual Term (in Years)	2 years 8 months 12 days	2 years 10 months 9 days
Vested and expected to vest at June 30, 2021 (in years)	2 years 8 months 12 days
Exercisable at June 30, 2021 (in years)	2 years 7 months 17 days
Options outstanding, Aggregate Intrinsic Value	$ 15,770	$ 41,673
Vested and expected to vest at June 30, 2021, Aggregate Intrinsic Value	15,766
Exercisable at June 30, 2021, Aggregate Intrinsic Value	$ 15,697