Customer and Geographic Information (Details) - USD ($)	3 Months Ended												12 Months Ended
	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type													100.00%	100.00%	100.00%
Net Sales	$ 167,435,000	$ 147,854,000	$ 133,731,000	$ 121,569,000	$ 147,762,000	$ 127,792,000	$ 139,028,000	$ 135,786,000	$ 152,377,000	$ 124,187,000	$ 70,323,000	$ 64,117,000	$ 570,589,000	$ 550,368,000	$ 411,004,000
U.S. government
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type													35.50%	32.70%	40.80%
Domestic
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type													38.90%	38.90%	29.20%
Total United States
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type													74.40%	71.60%	70.00%
International
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type													25.60%	28.40%	30.00%
Net Sales													$ 145,784,000	$ 156,483,000	$ 123,474,000
Verizon Communications Inc. | Customer Concentration Risk | Sales Revenue, Net
Revenue from External Customers [Line Items]
Concentration risk													10.00%