Computation of Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Oct. 27, 2012	Oct. 29, 2011
Basic earnings per unit
Net income	$ 11,861	$ 12,966
Weighted-average number of common shares (in shares)	33,089,959	33,508,193
Basic earnings per common share (in dollars per share)	$ 0.36	$ 0.39
Diluted earnings per unit
Weighted-average number of common shares (in shares)	33,089,959	33,508,193
Potential common stock arising from stock options, and unvested restricted share units (in shares)	631,111	708,258
Total shares-diluted (in shares)	33,721,070	34,216,451
Diluted earnings per common share	$ 0.35	$ 0.38
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	1,940,101	2,021,561