Stockholders' Equity Stock-Based Compensation Expense By Statement Of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	$ 21,462	$ 16,334	$ 9,347
Cost of service revenue
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	1,732	1,159	692
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	3,762	2,914	1,495
Sales and marketing
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	8,832	6,133	3,748
General and administrative
Stock-based employee compensation expense related to employee stock options and employee stock purchases, net of tax	$ 7,136	$ 6,128	$ 3,412