Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jul. 30, 2016	Apr. 23, 2016	Jan. 23, 2016	Oct. 24, 2015	Jul. 25, 2015	Apr. 25, 2015	Jan. 24, 2015	Oct. 25, 2014	Jul. 30, 2016	Jul. 25, 2015	Jul. 26, 2014	Sep. 15, 2015
Basic earnings per unit
Net income	$ 49,360	$ 33,083	$ 15,473	$ 30,824	$ 33,827	$ 20,258	$ 9,432	$ 20,807	$ 128,740	$ 84,324	$ 39,978
Weighted-average number of common shares (in shares)									32,315,636	34,045,481	33,773,158
Basic earnings per common share (in dollars per share)	$ 1.57	$ 1.02	$ 0.47	$ 0.94	$ 1.00	$ 0.59	$ 0.28	$ 0.61	$ 3.98	$ 2.48	$ 1.18
Diluted earnings per unit
Weighted-average number of common shares (in shares)									32,315,636	34,045,481	33,773,158
Potential common stock arising from stock options, and unvested restricted share units (in shares)									800,119	981,207	1,043,223
Total shares-diluted (in shares)									33,115,755	35,026,688	34,816,381
Diluted earnings per common share (in dollars per share)	$ 1.54	$ 1.00	$ 0.46	$ 0.91	$ 0.97	$ 0.58	$ 0.27	$ 0.59	$ 3.89	$ 2.41	$ 1.15
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)									10,076,982	103,896	586,389
Stock-based awards
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)									65,514	103,896	586,389
Convertible senior notes
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)									5,005,734	0	0
Warrants
Diluted earnings per unit
Anti-dilutive weighted shares excluded from the calculation of earnings per share (in shares)									5,005,734	0	0
Convertible Note Hedge
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%				0.75%	0.75%	0.75%
Debt Instrument, Convertible, Conversion Price												96.89
Class of Warrant or Right, Exercise Price of Warrants or Rights												$ 130.43