Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015 Location	Mar. 31, 2014	Mar. 31, 2013
Property Plant And Equipment [Line Items]
Manufacturing facility located	1
Product development Facility located	1
Age inventory showed little movement	5 years
Percentage of purchases scrapped	1.10%
Depreciation and amortization expense	$ 1,369,000	$ 1,351,000	$ 1,392,000
Expected net sale proceeds	3,800,000
Options excluded from the computation of diluted earnings per share	313,500	169,000	733,000
Engineering expense	6,607,000	8,162,000	9,377,000
Shipping and handling costs	267,000	266,000	202,000
Amount recognized in financial statement benefit of tax position	50.00%
Minimum
Property Plant And Equipment [Line Items]
Warranty for the equipment	1 year
Maximum
Property Plant And Equipment [Line Items]
Warranty for the equipment	3 years
Qualification Units
Property Plant And Equipment [Line Items]
Amortization of qualification units	671,000	339,000	73,000
Impairment of qualification units	0	399,000	106,000
Research and Development Costs
Property Plant And Equipment [Line Items]
Engineering expense	$ 5,344,000	$ 6,916,000	$ 7,664,000