NET LOSS PER SHARE - Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net loss available to common stockholders	$ (40,932)	$ (34,265)	$ (21,482)	$ (15,355)	$ (75,197)	$ (36,837)
Denominator:
Common shares - basic and diluted (in shares)	98,353		93,831		97,356	93,449
Net loss per share
Basic and diluted (in dollars per share)	$ (0.42)		$ (0.23)		$ (0.77)	$ (0.39)