Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Incentive Stock Plan
Shares authorized	4,384,814
Shares reserved for future issuance	4,466,805
Stock-Based Compensation Expense
Share-based compensation expense	$ 3,155	$ 2,596
Share-based compensation expense, net of tax	1,957	1,609
Unrealized compensation cost related to share-based compensation, pre tax	$ 19,450
Weighted average period remaining	2 years 6 months
Stock Options, Additional Disclosures
Proceeds from stock options exercised	$ 8,813	1,100
Fair value of options vested	2,794	$ 2,964
Service-Based RSUs, Additional Disclosures
Service-Based RSUs, Grants in Period, Weighted Average Grant Date Fair Value		$ 19.98
Service-Based RSUs, Nonvested, Aggregate Intrinsic Value,	22,774
Service-Based RSUs, Vested in Period, Fair Value	5,079	$ 1,419
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 2,894