Customer and Geographic Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2014	Apr. 30, 2013
Major customer
Revenues from External Customers
Percentage of revenue generated from external customer type	22.50%		16.30%
Minimum percentage of consolidated net sales sold to one customer or individual country requiring additional and separate disclosure	10.00%	10.00%	10.00%	10.00%
U.S. government
Revenues from External Customers
Percentage of revenue generated from external customer type	27.40%	36.90%	28.10%	38.10%
U.S. government | Excluding Mobile Data Communications segment
Revenues from External Customers
Percentage of revenue generated from external customer type	23.20%	30.20%	23.20%	31.10%
Commercial (United States)
Revenues from External Customers
Percentage of revenue generated from external customer type	10.30%	16.00%	12.90%	14.10%
Total United States
Revenues from External Customers
Percentage of revenue generated from external customer type	37.70%	52.90%	41.00%	52.20%
North African country
Revenues from External Customers
Percentage of revenue generated from external customer type	22.40%	4.00%	16.30%	4.70%
Other international
Revenues from External Customers
Percentage of revenue generated from external customer type	39.90%	43.10%	42.70%	43.10%
Total International
Revenues from External Customers
Percentage of revenue generated from external customer type	62.30%	47.10%	59.00%	47.80%
Revenue generated from external customers	$ 55,370,000	$ 32,907,000	$ 152,054,000	$ 112,596,000