Summary of Net Accounts Receivable Greater than or Equal to 10% of Net Account Receivable Balance (Detail) (Accounts Receivable, Credit Concentration Risk) (Detail) - Accounts Receivable - Credit Concentration Risk	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
L-3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of net accounts receivable		17.00%
Philips
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of net accounts receivable	14.00%	15.00%
GE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of net accounts receivable	11.00%