STOCK-BASED COMPENSATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 8,762	$ 7,903	$ 18,018	$ 16,316
Income tax benefit	(2,840)	(2,877)	(7,689)	(5,649)
Total stock-based compensation, net of tax	5,922	5,026	10,329	10,667
Cost of revenues [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	890	778	1,792	1,620
Research, development, and engineering [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	2,008	2,408	4,109	4,892
Selling, general, and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	5,864	4,717	12,117	9,804
Stock-based compensation expense included in operating expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 7,872	$ 7,125	$ 16,226	$ 14,696