Stock Repurchase Plan (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014	Jul. 31, 2014	Jul. 16, 2008	Mar. 09, 2006
Payments for Repurchase of Equity [Abstract]
Number of shares authorized to repurchase							3,000,000
Additional number of shares authorized to repurchase						3,000,000
Treasury Stock, Shares, Acquired	0	0	0	0
Number of shares repurchased since inception	4,949,111	4,949,111	4,949,111	4,949,111	4,949,111
Value of stock repurchased since inception	$ (193,192)	$ (193,192)	$ (193,192)	$ (193,192)	$ (193,192)
Remaining shares available for repurchase under existing program	1,050,889		1,050,889