Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized	2,392,904		2,392,904
Shares reserved for future issuance	3,679,698		3,679,698
Share-based compensation expense	$ 3,603	$ 2,153	$ 7,805	$ 5,897
Share-based compensation expense (net of tax)	3,150	$ 1,614	6,896	$ 4,423
Unrecognized compensation cost related to share-based compensation, pre tax	$ 13,910		$ 13,910
Weighted average period remaining			1 year 11 months 1 day
Options Outstanding, Exercisable	1,378,591	1,962,475	1,378,591	1,962,475
Options Outstanding, Exercisable, Weighted Average Exercise Price	$ 26.87	$ 26.61	$ 26.87	$ 26.61
Proceeds from stock options exercised	$ 5,179	$ 6,699	$ 17,317	$ 9,948
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	993	512	3,349	895
Intrinsic value of stock options exercised	13,394	2,935
Fair value of stock options vested	2,849	$ 3,004
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value			5,125	$ 5,002
Aggregate intrinsic value of unvested service and performance-based RSUs outstanding and expected to vest	$ 19,510		$ 19,510