Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Incentive Stock Plan
Shares authorized	3,672,332
Shares reserved for future issuance	3,989,341
Stock-Based Compensation Expense
Share-based compensation expense	$ 3,744	$ 3,155
Share-based compensation expense, net of tax	2,321	1,957
Unrealized compensation cost related to share-based compensation, pre tax	$ 17,077
Weighted average period remaining	2 years 1 month 6 days
Stock Options, Additional Disclosures
Proceeds from stock options exercised	$ 3,249	8,813
Fair value of options vested	2,974	2,794
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	478	1,100
Service-Based RSUs, Additional Disclosures
Service-Based RSUs, Nonvested, Aggregate Intrinsic Value,	22,077
Service-Based RSUs, Vested in Period, Fair Value	4,736	5,079
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 1,257	$ 2,894
Service Based Restricted Shares and Restricted Stock Units [Member]
Service-Based RSUs, Additional Disclosures
Service-Based RSUs, Grants in Period, Weighted Average Grant Date Fair Value	$ 36.65	$ 35.14