Accounts Receivable (Details) (USD $)	Oct. 31, 2012	Jul. 31, 2012
Total accounts receivable	$ 48,292,000	$ 57,830,000
Less: Allowance for doubtful accounts	1,365,000	1,588,000
Accounts receivable, net	46,927,000	56,242,000
Unbilled receivables on contracts-in-progress due from U.S. government and its agencies	2,053,000	3,320,000
Retainage included in unbilled receivables	13,000	13,000
Billed Receivables [Member] | Commercial Customers [Member]
Total accounts receivable	35,209,000	41,139,000
Billed Receivables [Member] | U.S. Government and Its Agencies [Member]
Total accounts receivable	9,013,000	11,927,000
Unbilled Receivables on Contracts-In-Progress [Member]
Total accounts receivable	$ 4,070,000	$ 4,764,000