Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 29, 2017	Apr. 23, 2016	Apr. 29, 2017	Apr. 23, 2016	Sep. 15, 2015
Basic earnings per unit
Net income	$ 38,796	$ 33,083	$ 113,509	$ 79,380
Weighted-average number of common shares (in shares)	31,357,124	32,433,560	31,439,981	32,656,490
Basic earnings per common share (in dollars per share)	$ 1.24	$ 1.02	$ 3.61	$ 2.43
Diluted earnings per unit
Weighted-average number of common shares (in shares)	31,357,124	32,433,560	31,439,981	32,656,490
Potential common stock arising from stock options, and unvested restricted share units (in shares)	552,802	617,374	651,110	830,025
Total shares-diluted (in shares)	31,909,926	33,050,934	32,091,091	33,486,515
Diluted earnings per common share (in dollars per share)	$ 1.22	$ 1.00	$ 3.54	$ 2.37
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	10,107,488	10,128,012	10,076,100	10,091,260
Convertible Note Hedge
Diluted earnings per unit
Debt Instrument, Convertible, Conversion Price (per share)	$ 96.89		$ 96.89		$ 96.89
0.75% Convertible Senior Notes Due 2021
Diluted earnings per unit
Debt Instrument, Convertible, Conversion Price (per share)					96.89
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 130.43		$ 130.43		$ 130.43
Stock-based awards
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	96,020	116,544	64,632	79,792
Convertible senior notes
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	5,005,734	5,005,734	5,005,734
Warrants
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	5,005,734	5,005,734	5,005,734