STOCK PLANS - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 50,861	$ 56,328	$ 47,317
Cost of product revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	1,069	1,463	1,159
Cost of service revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	5,774	5,959	4,824
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	15,511	17,321	14,711
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	17,085	18,923	15,213
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 11,422	$ 12,662	$ 11,410