Common Stock Repurchases - Additional Information (Detail) - 2016 Repurchase program - USD ($)	3 Months Ended	17 Months Ended
	Oct. 31, 2017	Oct. 31, 2017	May 26, 2016
Stockholders Equity Note [Line Items]
Amount authorized for repurchase of Company's common stock			$ 15,000,000
Repurchase of common stock (in shares)	13,489	61,197
Repurchase of common stock	$ 1,000,000	$ 4,400,000
Average purchase price of common stock	$ 70.52	$ 71.10