Common Stock Repurchases - Additional Information (Detail) (USD $)	12 Months Ended			3 Months Ended	12 Months Ended		12 Months Ended			12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2012 2010 Repurchase program	Jul. 31, 2012 2010 Repurchase program	Dec. 09, 2010 2010 Repurchase program Maximum	Jul. 31, 2014 2011 Repurchase program	Jul. 31, 2013 2011 Repurchase program	Dec. 08, 2011 2011 Repurchase program Maximum	Jul. 31, 2014 2011 Cumulative repurchase program	Jul. 31, 2014 2014 Repurchase program	Jun. 02, 2014 2014 Repurchase program Maximum
Stockholders Equity Note [Line Items]
Amount authorized for repurchase of Company's common stock						$ 30,000,000			$ 30,000,000			$ 30,000,000
Repurchase of common stock (in shares)				586,679	286,390		166,361	111,816		415,768	18,683
Repurchase of common stock	$ 14,959,000	$ 7,945,000	$ 23,260,000	$ 30,000,000	$ 14,800,000		$ 13,500,000	$ 7,900,000		$ 30,000,000	$ 1,400,000
Average purchase price of common stock				$ 51.14	$ 51.73		$ 81.33	$ 71.06		$ 71.98	$ 76.22