Accounts Receivable (Details) (USD $)	9 Months Ended	12 Months Ended
	Apr. 30, 2015	Jul. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	68,378,000	55,514,000
Less allowance for doubtful accounts	757,000	627,000
Accounts receivable, net	67,621,000	54,887,000
Accounts Receivable | Major customer | U.S. Prime Contractor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of total accounts receivable	41.00%	18.00%
Billed Receivables | Commercial Customers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	27,340,000	31,681,000
Billed Receivables | U.S. Government and Its Agencies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	11,259,000	10,316,000
Unbilled Receivables on Contracts-In-Progress
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	29,779,000	13,517,000
Unbilled receivables on contracts-in-progress due from U.S. government and its agencies	1,242,000	770,000
Retainage included in unbilled receivables	0	120,000
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	27,990,000	9,990,000