Accounts Receivable (Details) (USD $)	Jul. 31, 2011	Jul. 31, 2010
Total accounts receivable	$ 72,021,000	$ 136,967,000
Less: Allowance for doubtful accounts	1,220,000	1,127,000
Accounts receivable, net	70,801,000	135,840,000
Unbilled receivables on contracts-in-progress due from U.S. government and its agencies	4,487,000	11,430,000
Retainage included in unbilled receivables	28,000	28,000
Billed Receivables [Member] | U.S. Government and its agencies [Member]
Total accounts receivable	22,075,000	89,843,000
Billed Receivables [Member] | Non-United States Government Customer [Member]
Total accounts receivable	38,245,000	35,230,000
Unbilled Receivables on Contracts-In-Progress [Member]
Total accounts receivable	$ 11,701,000	$ 11,894,000