Stockholders' Equity Stock-Based Compensation Expense By Statement Of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	$ 29,176	$ 21,462	$ 16,334
Cost of service revenue
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	1,821	1,732	1,159
Cost of product revenue
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	0	0	0
Research and development
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	6,418	3,762	2,914
Sales and marketing
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	11,654	8,832	6,133
General and administrative
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	$ 9,283	$ 7,136	$ 6,128