Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended	3 Months Ended	6 Months Ended
	Oct. 31, 2012 Customer Segment	Oct. 31, 2011 Customer	Apr. 30, 2012 Reclassifications	Oct. 31, 2011 Increase (Decrease) Effect of Exchange Rates on Cash	Jan. 31, 2012 Increase (Decrease) Effect of Exchange Rates on Cash	Oct. 31, 2011 Increase (Decrease) Net Cash Provided By Used In Operating Activities	Jan. 31, 2012 Increase (Decrease) Net Cash Provided By Used In Operating Activities	Jan. 31, 2012 Increase (Decrease) Net Cash Provided By Used In Financing Activities	Oct. 31, 2012 Minimum	Oct. 31, 2012 Maximum	Oct. 31, 2012 Philips	Jul. 31, 2012 Philips	Oct. 31, 2012 L-3	Jul. 31, 2012 L-3	Oct. 31, 2012 General Electric Corporation	Jul. 31, 2012 General Electric Corporation
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number Of Operating Segments	3
Percentage of total net revenue	71.00%	62.00%
Number of customers accounting for more than 10 percent of total revenue	3	3
Percentage of net accounts receivable											18.00%	13.00%	11.00%	18.00%	12.00%	10.00%
Ownership interests									10.00%	50.00%
Effect of exchange rate on cash	$ 529	$ (418)	$ 620
Prior period reclassification adjustment				$ 910	$ 620	$ (910)	$ (654)	$ 34