Common Stock Repurchases - Additional Information (Detail) - 2016 Repurchase program - USD ($)	3 Months Ended	6 Months Ended	20 Months Ended
	Jan. 31, 2018	Jan. 31, 2018	Jan. 31, 2018	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)	0	13,489	61,197
Repurchase of common stock		$ 1,000,000	$ 4,400,000
Average purchase price of common stock		$ 70.52	$ 71.07