Accounts Receivable (Details) (USD $)	Oct. 31, 2011	Jul. 31, 2011
Total accounts receivable	$ 75,643,000	$ 72,021,000
Less: Allowance for doubtful accounts	1,171,000	1,220,000
Accounts receivable, net	74,472,000	70,801,000
Unbilled receivables on contracts-in-progress due from U.S. government and its agencies	2,948,000	4,487,000
Retainage included in unbilled receivables	28,000	28,000
Billed Receivables [Member] | Non-United States Government Customer [Member]
Total accounts receivable	44,055,000	38,245,000
Billed Receivables [Member] | U.S. Government and its agencies [Member]
Total accounts receivable	22,148,000	22,075,000
Unbilled Receivables on Contracts-In-Progress [Member]
Total accounts receivable	$ 9,440,000	$ 11,701,000