INCOME TAXES (Details) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Deferred [Abstract]
Total deferred income tax provision (benefit)	$ (3,954,000)	$ (785,000)	$ (1,307,000)
Total income tax provision	12,239,000	8,993,000	17,149,000
Income before income taxes [Abstract]
Federal statutory income tax rate (in hundredths)	35.00%
Income Tax Provision Reconciliation [Abstract]
Income taxes at federal income tax rate	11,565,000	8,828,000	16,896,000
State income taxes, net of federal benefits	787,000	475,000	1,282,000
Non-deductible compensation	880,000	260,000	56,000
Research and development tax credits	(383,000)	(210,000)	(541,000)
Tax-exempt interest income	(6,000)	(20,000)	(32,000)
Qualified production activities income benefit	(866,000)	(490,000)	(525,000)
Other	262,000	150,000	13,000
Total income tax provision	12,239,000	8,993,000	17,149,000
Excess tax benefits from share-based awards and other tax adjustments	946,000	2,164,000	2,683,000
Cumulative foreign earnings upon which U.S. income taxes has not been provided	200,000
U.S. tax liability if earnings were repatriated	84,000
Breakdown Between Current and Non-current Deferred Tax Assets (Liabilities) [Abstract]
Deferred tax assets, current	6,575,000	4,464,000
Deferred tax assets, non-current	3,413,000	1,557,000
Deferred tax liabilities, non-current	(310,000)	0
Total net deferred tax assets	9,678,000	6,021,000
Deferred tax assets:
Research and development tax credit carryforwards	717,000	646,000
Capitalized research and development	106,000	136,000
Inventory reserves	724,000	622,000
Deferred revenue from extended maintenance agreements	1,687,000	1,940,000
Warranty reserves	1,190,000	704,000
Accrued payroll and other accrued expenses	2,904,000	1,269,000
Share-based compensation	2,932,000	2,129,000
Alternative minimum tax credits	24,000	24,000
Tax on deferred intercompany profit	1,161,000	742,000
Other	494,000	792,000
Total deferred tax assets	11,939,000	9,004,000
Deferred tax liabilities:
Depreciation	(1,850,000)	(2,876,000)
Other	(411,000)	(107,000)
Total deferred tax liabilities	(2,261,000)	(2,983,000)
Net deferred tax assets	9,678,000	6,021,000
Valuation allowance	0	0	0
Income Tax Contingency [Line Items]
Penalties and interest related to unrecognized tax benefits	0	0	0
Federal [Member]
Income Tax Contingency [Line Items]
Statute of limitations	3 years
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	0
Federal [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2012
Federal [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2015
State of California [Member]
Income Tax Contingency [Line Items]
Statute of limitations	4 years
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	0
Tax Credit Carryforward [Line Items]
Tax credit carryforward with indefinite life	1,100,000
State of California [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2011
State of California [Member] | Minimum [Member] | Research and Development Tax Credit [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2007
State of California [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2015
State of California [Member] | Maximum [Member] | Research and Development Tax Credit [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2015
Germany [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2012
Germany [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2015
United Kingdom [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2011
United Kingdom [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2015
Continuing Operations [Member]
Current [Abstract]
Federal	12,065,000	7,947,000	16,635,000
State	1,657,000	939,000	1,647,000
Foreign	64,000	892,000	174,000
Total current income tax provision	13,786,000	9,778,000	18,456,000
Deferred [Abstract]
Federal	(1,363,000)	(631,000)	(1,219,000)
State	(158,000)	(154,000)	(88,000)
Foreign	(26,000)	0	0
Total deferred income tax provision (benefit)	(1,547,000)	(785,000)	(1,307,000)
Total income tax provision	12,239,000	8,993,000	17,149,000
Income before income taxes [Abstract]
United States	33,489,000	22,598,000	47,630,000
Foreign	(447,000)	2,624,000	646,000
Income before tax provision	33,042,000	25,222,000	48,276,000
Income Tax Provision Reconciliation [Abstract]
Total income tax provision	12,239,000	8,993,000	17,149,000
Discontinued Operations [Member]
Current [Abstract]
Federal	5,923,000	(1,147,000)	(2,060,000)
State	458,000	(88,000)	(159,000)
Total current income tax provision	6,381,000	(1,235,000)	(2,219,000)
Deferred [Abstract]
Federal	(2,258,000)	0	0
State	(175,000)	0	0
Total deferred income tax provision (benefit)	(2,433,000)	0	0
Total income tax provision	3,948,000	(1,235,000)	(2,219,000)
Income before income taxes [Abstract]
United States	10,475,000	(3,279,000)	(5,887,000)
Income Tax Provision Reconciliation [Abstract]
Total income tax provision	$ 3,948,000	$ (1,235,000)	$ (2,219,000)