Computation of Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 25, 2014	Jan. 26, 2013	Jan. 25, 2014	Jan. 26, 2013
Basic earnings per unit
Net income	$ (3,067)	$ 1,463	$ 15,593	$ 13,323
Weighted-average number of common shares (in shares)	33,836,099	32,780,667	33,629,884	32,935,305
Basic earnings per common share	$ (0.09)	$ 0.04	$ 0.46	$ 0.40
Diluted earnings per unit
Weighted-average number of common shares (in shares)	33,836,099	32,780,667	33,629,884	32,935,305
Potential common stock arising from stock options, and unvested restricted share units (in shares)	0	733,749	1,138,061	671,875
Total shares-diluted (in shares)	33,836,099	33,514,416	34,767,945	33,607,180
Diluted earnings per common share	$ (0.09)	$ 0.04	$ 0.45	$ 0.40
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	3,440,300	1,289,661	753,914	1,483,241