Stockholders' Equity - Additional Information (Detail) - USD ($)		12 Months Ended
	May 15, 2015	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Stock Based Compensation And Stockholders Equity [Line Items]
Common stock purchased, shares	1,000,000
Common stock price per share	$ 60.00
Aggregate purchase price of common stock	$ 60,000,000		$ 60,000,000
Closing price of common stock	$ 61.29
Percentage of issued and outstanding common stock prior to repurchase	1.90%
Option expiration from the date of grant, in years		10 years
Options granted during the period		0	0	0
Cash received from stock option exercises		$ 0	$ 141,000	$ 3,206,000
Total intrinsic value of stock options exercised		0	$ 168,000	$ 2,597,000
Stock option exercised			5,000	101,313
Stock option value exercised			$ 141,000	$ 3,206,000
Total unrecognized compensation costs		$ 11,077,000
Period for recognition of compensation cost not yet recognized		2 years 5 months 5 days
Stock-based compensation		$ 9,387,000	6,776,000	5,231,000
Tax benefits from stock compensation expense		3,473,000	2,507,000	1,925,000
Discontinued Operations
Stock Based Compensation And Stockholders Equity [Line Items]
Total compensation expenses		$ 0	0	480,000
Minimum
Stock Based Compensation And Stockholders Equity [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		3 years
Maximum
Stock Based Compensation And Stockholders Equity [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		5 years
Stock Option Awards
Stock Based Compensation And Stockholders Equity [Line Items]
Total compensation expenses		$ 0	0	0
Restricted Stock Awards
Stock Based Compensation And Stockholders Equity [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period		5 years
Total compensation expenses		$ 115,000	115,000	91,000
Total unrecognized compensation costs		$ 101,000
Period for recognition of compensation cost not yet recognized		11 months 23 days
2010 Equity Incentive Plan
Stock Based Compensation And Stockholders Equity [Line Items]
Number of shares authorized under stock option plan		2,000,000
Number of shares available to be granted		1,211,385
2006 Equity Incentive Plan
Stock Based Compensation And Stockholders Equity [Line Items]
Number of shares authorized under stock option plan		1,100,000
Number of shares available to be granted		30,000
Restricted Stock Units (RSUs)
Stock Based Compensation And Stockholders Equity [Line Items]
Total compensation expenses		$ 9,272,000	$ 6,661,000	$ 5,140,000