Income Taxes (Schedule Of Differences Between Statutory Tax Rate And Effective Tax Rate) (Details)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income Tax Expense Reconciliation [Line Items]
Statutory federal tax expense (benefit) rate	21.00%	31.50%	35.00%
State taxes, net of federal benefit	0.70%	0.80%	1.00%
Differences between statutory rate and foreign effective tax rate	(14.40%)	(19.10%)	(19.30%)
Effective Income Tax Rate Reconciliation US Tax Reform Act 2017	(0.40%)	16.20%	0.00%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(1.90%)	(3.00%)	0.00%
Research and development credits	(2.40%)	(1.40%)	(0.70%)
Unremitted earnings of foreign subsidiaries			2.20%
Non-deductible stock-based compensation	2.30%	2.70%	2.30%
Other	0.70%	0.30%	(0.40%)
Effective tax expense (benefit) rate	5.60%	28.00%	20.10%