Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Incentive Stock Plan
Shares authorized	2,682,634
Shares reserved for future issuance	3,655,246
Stock-Based Compensation Expense
Share-based compensation expense	$ 4,965	$ 3,744
Share-based compensation expense, net of tax	4,319	2,321
Unrealized compensation cost related to share-based compensation, pre tax	$ 16,245
Weighted average period remaining	2 years 1 month 6 days
Stock Options, Additional Disclosures
Proceeds from stock options exercised	$ 12,138	3,249
Fair value of options vested	2,798	2,974
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	2,356	478
Service-Based RSUs, Additional Disclosures
Service-Based RSUs, Nonvested, Aggregate Intrinsic Value,	18,497
Service-Based RSUs, Vested in Period, Fair Value	4,795	4,736
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 9,423	$ 1,257
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	$ 44.04	$ 35.14