INCOME TAXES (Details) - USD ($)		12 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Current:
Federal		$ (1,199,000)	$ 82,523,000	$ 10,591,000
State		2,550,000	4,274,000	457,000
Foreign		(1,550,000)	6,860,000	7,731,000
Total current provision for income taxes		(199,000)	93,657,000	18,779,000
Deferred:
Federal		(37,577,000)	9,002,000	1,022,000
State		(4,160,000)	(1,585,000)	(117,000)
Foreign		(8,195,000)	22,000	(618,000)
Total deferred benefit for income taxes		(49,932,000)	7,439,000	287,000
Income tax expense (benefit)		(50,131,000)	101,096,000	19,066,000
Components of income before income taxes
United States		(179,387,000)	17,654,000	43,377,000
Foreign		(6,305,000)	82,573,000	58,288,000
Income (loss) before income taxes		(185,692,000)	100,227,000	101,665,000
Reconciliation between statutory federal income taxes and income tax expense
Tax expense at statutory rate		(38,995,000)	31,631,000	35,583,000
Foreign operations taxed at different rates		(4,965,000)	(17,970,000)	(13,183,000)
State taxes, net of federal benefit		(1,610,000)	2,689,000	340,000
Research and development credit		(4,288,000)	(2,023,000)	(3,119,000)
Net GILTI Inclusion		4,398,000	0	0
Net GILTI Inclusion		(1,196,000)	(1,771,000)	(365,000)
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount		(3,728,000)	87,790,000	0
Other, net		253,000	750,000	(190,000)
Income tax expense (benefit)		(50,131,000)	101,096,000	19,066,000
Components of Deferred Tax Assets
Accruals and other reserves		24,167,000	4,809,000
Deferred compensation		2,980,000	3,467,000
Net operating loss carry forward		16,921,000	1,540,000
Stock compensation		9,484,000	8,384,000
Interest expense		11,550,000	0
Tax credits		7,072,000	6,504,000
Deferred Tax Assets, Engineering Costs		31,015,000	0
Other deferred tax assets		635,000	1,070,000
Valuation allowance		(15,787,000)	(2,514,000)
Total deferred tax assets		88,037,000	23,260,000
Components of Deferred Tax Liabilities
Deferred gains on sales of properties		(1,155,000)	(1,160,000)
Deferred Tax Liabilities, Intangible Assets		(92,544,000)	0
Deferred Tax Liabilities, Unearned Revenue		(5,054,000)	0
Unremitted earnings of certain subsidiaries		(17,879,000)	(1,976,000)
Fixed asset depreciation		(7,881,000)	(4,150,000)
Total deferred tax liabilities	[1]	(36,476,000)
Deferred Tax Assets, Gross		124,513,000	7,286,000
Net deferred tax assets	[1]		15,974,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period		12,612,000	12,854,000	12,692,000
Increase (decrease) of unrecognized tax benefits related to prior fiscal years		254,000	(1,310,000)	(2,000)
Unrecognized Tax Benefits, Increase Resulting from Acquisition		13,329,000	0	0
Increase of unrecognized tax benefits related to the current year		2,069,000	3,085,000	2,195,000
Reductions to unrecognized tax benefits related to settlements with taxing authorities		0	(115,000)	0
Reductions to unrecognized tax benefits related to lapse of applicable statute of limitations		(1,806,000)	(1,902,000)	(2,031,000)
Balance at end of period		26,458,000	12,612,000	12,854,000
Tax penalties accrued			0	$ 0
Interest related to unrecognized tax benefits		2,000,000	1,400,000
Unrecognized Tax Benefits, Period Increase (Decrease)		1,200,000
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)			79,700,000
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Transition Tax on Accumulated Foreign Earnings, Amount		(800,000)
Payment For Repatriation Tax		21,500,000
Tax Cuts And Jobs Act, Transition Tax For Accumulated Foreign Earnings, Liability		57,300,000
Tax Cuts And Jobs Act, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Income Tax Expense			$ 5,000,000
Tax Cuts And Jobs Act, Transition Tax For Accumulated Foreign Earnings, Income Tax Expense		$ (3,200,000)
Effective Income Tax Rate Reconciliation, Change In Enacted Tax Rate, Increase (Decrease) In Global Tax Rate, Percent		(2.10%)
California Franchise Tax Board [Member]
Components of Deferred Tax Liabilities
Research and development credit carryforwards		$ 11,700,000
State Administration of Taxation, China [Member]
Components of Deferred Tax Assets
Net operating loss carry forward		300,000
Foreign Tax Authority [Member]
Components of Deferred Tax Assets
Net operating loss carry forward		9,800,000
State and Local Jurisdiction [Member]
Components of Deferred Tax Assets
Net operating loss carry forward		5,700,000
Domestic Tax Authority [Member]
Components of Deferred Tax Assets
Net operating loss carry forward		$ 3,900,000

[1] The Company's deferred tax assets for the Fiscal Year ended March 31, 2018 and March 31, 2019, are included as a component of other assets on the consolidated balance sheets.