Stock Repurchase Plan (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015	Dec. 04, 2015	Jul. 31, 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	108,036	0	485,866	0
Payments for Repurchase of Common Stock	$ 13,800		$ 53,787	$ 0
Number of shares repurchased since inception	5,434,977	4,949,111	5,434,977	4,949,111		4,949,111
Value of stock repurchased since inception	$ (246,979)	$ (193,192)	$ (246,979)	$ (193,192)		$ (193,192)
Remaining shares available for repurchase under existing program	2,065,023		2,065,023