Computation of Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Oct. 26, 2013	Oct. 27, 2012
Basic earnings per unit
Net income	$ 18,660	$ 11,861
Weighted-average number of common shares (in shares)	33,423,678	33,089,959
Basic earnings per common share	$ 0.56	$ 0.36
Diluted earnings per unit
Weighted-average number of common shares (in shares)	33,423,678	33,089,959
Potential common stock arising from stock options, and unvested restricted share units (in shares)	1,215,320	631,111
Total shares-diluted (in shares)	34,638,998	33,721,070
Diluted earnings per common share	$ 0.54	$ 0.35
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	547,154	1,940,101