Computation of Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 26, 2013	Jan. 28, 2012	Jan. 26, 2013	Jan. 28, 2012
Basic earnings per unit
Net income	$ 1,463	$ 3,485	$ 13,323	$ 16,451
Weighted-average number of common shares (in shares)	32,780,667	33,759,015	32,935,305	33,633,596
Basic earnings per common share	$ 0.04	$ 0.10	$ 0.40	$ 0.49
Diluted earnings per unit
Weighted-average number of common shares (in shares)	32,780,667	33,759,015	32,935,305	33,633,596
Potential common stock arising from stock options, and unvested restricted share units (in shares)	733,749	877,505	671,875	797,823
Total shares-diluted (in shares)	33,514,416	34,636,520	33,607,180	34,431,419
Diluted earnings per common share	$ 0.04	$ 0.10	$ 0.40	$ 0.48
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	1,289,661	1,220,534	1,483,241	2,011,358