Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jan. 31, 2013 Customer	Jan. 31, 2012 Customer	Jan. 31, 2013 Segment Customer	Jan. 31, 2012 Customer	Apr. 30, 2012 Reclassifications	Jan. 31, 2012 Increase (Decrease) Effect of Exchange Rates on Cash	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	Jan. 31, 2013 Minimum	Jan. 31, 2013 Maximum	Jan. 31, 2013 Philips	Jul. 31, 2012 Philips	Jan. 31, 2013 L-3	Jul. 31, 2012 L-3	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	67.00%	64.00%	69.00%	65.00%
Number of customers accounting for more than 10 percent of total revenue	3	2	3	3
Percentage of net accounts receivable											13.00%	13.00%	16.00%	18.00%	10.00%
Ownership interests									10.00%	50.00%
Effect of exchange rate on cash			$ 1,166	$ (1,049)	$ 620
Prior period reclassification adjustment						$ 620	$ (654)	$ 34