Computation of Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 25, 2015	Apr. 26, 2014	Apr. 25, 2015	Apr. 26, 2014
Basic earnings per unit
Net income	$ 20,258	$ 7,895	$ 50,497	$ 23,488
Weighted-average number of common shares (in shares)	34,107,262	33,860,832	34,081,381	33,707,957
Basic earnings (loss) per common share (in dollars per share)	$ 0.59	$ 0.23	$ 1.48	$ 0.70
Diluted earnings per unit
Weighted-average number of common shares (in shares)	34,107,262	33,860,832	34,081,381	33,707,957
Potential common stock arising from stock options, and unvested restricted share units (in shares)	921,694	902,203	1,010,263	1,059,443
Total shares-diluted (in shares)	35,028,956	34,763,035	35,091,644	34,767,400
Diluted earnings (loss) per common share (in dollars per share)	$ 0.58	$ 0.23	$ 1.44	$ 0.68
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	158,113	576,257	159,484	570,859