Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 23, 2016	Apr. 25, 2015	Apr. 23, 2016	Apr. 25, 2015	Sep. 15, 2015	Jul. 25, 2015
Basic earnings per unit
Net income	$ 33,083	$ 20,258	$ 79,380	$ 50,497
Weighted-average number of common shares (in shares)	32,433,560	34,107,262	32,656,490	34,081,381
Basic earnings (loss) per common share (in dollars per share)	$ 1.02	$ 0.59	$ 2.43	$ 1.48
Diluted earnings per unit
Weighted-average number of common shares (in shares)	32,433,560	34,107,262	32,656,490	34,081,381
Potential common stock arising from stock options, and unvested restricted share units (in shares)	617,374	921,694	830,025	1,010,263
Total shares-diluted (in shares)	33,050,934	35,028,956	33,486,515	35,091,644
Diluted earnings (loss) per common share (in dollars per share)	$ 1.00	$ 0.58	$ 2.37	$ 1.44
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	10,128,012	158,113	10,091,260	159,484
Stock Compensation Plan [Member]
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	116,544	158,113	79,792	159,484
Convertible Debt Securities [Member]
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	0	5,005,734	0
Note Warrant [Member]
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)	5,005,734	0	5,005,734	0
Convertible Note Hedge [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt Instrument, Convertible, Conversion Price					$ 96.89
0.75% Convertible Senior Notes Due 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt, interest rate (in percent)	0.75%		0.75%			0.00%
Debt Instrument, Convertible, Conversion Price					96.89
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 130.43