Accounts Receivable (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jan. 31, 2016	Jul. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 55,430,000	$ 70,461,000
Less allowance for doubtful accounts	1,681,000	1,206,000
Accounts receivable, net	$ 53,749,000	$ 69,255,000
Accounts Receivable | Major customer | U.S. Prime Contractor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total accounts receivable	17.20%	36.30%
Billed Receivables | Commercial Customers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 27,677,000	$ 39,062,000
Billed Receivables | U.S. Government and Its Agencies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	15,124,000	8,375,000
Unbilled Receivables on Contracts-In-Progress
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	12,629,000	23,024,000
Unbilled receivables on contracts-in-progress due from U.S. government and its agencies	1,070,000	1,126,000
Retainage included in unbilled receivables	0	0
Unbilled Receivables on Contracts-In-Progress | Major customer | U.S. Prime Contractor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivable related to our large over-the-horizon microwave system contracts	$ 9,396,000	$ 20,256,000