Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 20.07
Shares authorized	3,784,771		3,784,771
Shares reserved for future issuance	4,477,197		4,477,197
Share-based compensation expense	$ 2,238	$ 1,973	$ 5,394	$ 4,569
Share-based compensation expense (net of tax)	1,387	$ 1,223	3,344	$ 2,833
Unrecognized compensation cost related to share-based compensation, pre tax	$ 17,455		$ 17,455
Weighted average period remaining			2 years 3 months 18 days
Options Outstanding, Exercisable	2,037,018	2,723,184	2,037,018	2,723,184
Options Outstanding, Exercisable, Weighted Average Exercise Price	$ 28.67	$ 30.00	$ 28.67	$ 30.00
Proceeds from stock options exercised	$ 5,846	$ 53	$ 14,659	$ 53
Tax benefit on stock options exercised	353	3	1,453	3
Intrinsic value of stock options exercised	6,719	7
Fair value of stock options vested	2,890	$ 3,131
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value			4	$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested	$ 25		$ 25
Service Based Restricted Shares and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 35.12