STOCK-BASED COMPENSATION: - Effect of stock-based compensation expense on income, by financial statement line item (Details) - USD ($) $ in Millions	9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based compensation
Total non-cash stock-based compensation	$ 64.6	$ 72.3
Cost of revenue
Share-based compensation
Total non-cash stock-based compensation	2.7	2.8
Research and development
Share-based compensation
Total non-cash stock-based compensation	21.0	17.3
Sales and marketing
Share-based compensation
Total non-cash stock-based compensation	25.6	34.4
General and administrative
Share-based compensation
Total non-cash stock-based compensation	$ 15.3	$ 17.8