Accounts Receivable (Tables)

9 Months Ended

Apr. 30, 2012

Accounts Receivable [Abstract]

Accounts receivable

	April 30, 2012	July 31, 2011
Billed receivables from commercial customers	$    34,429,000	38,245,000
Billed receivables from the U.S. government and its agencies	33,533,000	22,075,000
Unbilled receivables on contracts-in-progress	6,187,000	11,701,000
Total accounts receivable	74,149,000	72,021,000
Less allowance for doubtful accounts	1,140,000	1,220,000
Accounts receivable, net	$    73,009,000	70,801,000