Share Repurchase Program (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2017	Apr. 30, 2016	Jul. 31, 2016	Dec. 04, 2015	Jul. 16, 2008	Mar. 09, 2006
Accelerated Share Repurchases [Line Items]
Number of shares authorized to repurchase	7,500,000		7,500,000					3,000,000
Additional number of shares authorized to repurchase						1,500,000	3,000,000
Treasury Stock, Shares, Acquired	0	108,036	1,317	485,866
Payments for Repurchase of Common Stock		$ 13,800	$ 210	$ 53,787
Number of shares repurchased since inception	5,436,294	5,434,977	5,436,294	5,434,977	5,434,977
Value of stock repurchased since inception	$ 247,189	$ 246,979	$ 247,189	$ 246,979	$ 246,979
Remaining shares available for repurchase under existing program	2,063,706		2,063,706