Long-Term Debt and Credit Arrangements - Narrative (Details)				3 Months Ended		12 Months Ended
	Feb. 09, 2016 USD ($)	Oct. 21, 2015 USD ($)	Jan. 02, 2014 USD ($)	Jul. 29, 2016 USD ($)	Jul. 24, 2015 USD ($)	Apr. 29, 2016 USD ($)	Jul. 25, 2014 USD ($)
Line of Credit Facility [Line Items]
Total borrowings				$ 364,555,000		$ 339,057,000
Revolving credit facility, maximum borrowing capacity		$ 750,000,000
Amortization of debt issuance costs			$ 2,064,000		$ 1,705,000
Revolving credit facility (up to)		650,000,000
Line of credit facility, amount outstanding		50,000,000
Additional indebtedness allowed (up to)		300,000,000
Line of credit facility, borrowing increase		$ 950,000,000
Credit facility unused capacity commitment fee percentage low end of range		0.15%
Credit facility unused capacity commitment fee percentage high end of range		0.25%
Debt instrument, fee amount		$ 812,000
Write off of deferred debt issuance cost		$ 480,000
Sale leaseback credit agreement availability				$ 51,000,000
Effective interest rate				2.48%	2.21%
Capitalized interest costs				$ 198,000	$ 11,000
Interest paid				$ 2,203,000	$ 2,738,000
LIBOR
Line of Credit Facility [Line Items]
Credit facility variable rate low end		1.00%
Credit facility variable rate high end		2.75%
Debt instrument, basis spread on variable rate		1.00%
Base Rate
Line of Credit Facility [Line Items]
Credit facility variable rate low end		0.00%
Credit facility variable rate high end		1.75%
Federal Funds Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.50%	0.50%
Eurodollar
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.00%
First Amendment to the Credit Agreement
Line of Credit Facility [Line Items]
Share repurchase restriction, credit agreement covenant		$ 150,000,000
Rent expense coverage ratio		6
First Amendment to the Credit Agreement | Credit Agreement borrowings
Line of Credit Facility [Line Items]
Unamortized debt financing cost							$ 1,279,000
Credit agreement, sale leaseback capacity		$ 100,000,000
Coverage ratio requirement (not less than)				3.00
Leverage ratio requirement (not to exceed)				4.25
Current coverage ratio				11.82
Current leverage ratio				2.78
Third Amendment to the Credit Agreement
Line of Credit Facility [Line Items]
Credit agreement, sale leaseback capacity				$ 300,000,000
Third Amendment to the Credit Agreement | Credit Agreement borrowings
Line of Credit Facility [Line Items]
Credit agreement, sale leaseback capacity		$ 300,000,000
Credit Agreement borrowings
Line of Credit Facility [Line Items]
Total borrowings				333,337,000		307,000,000
Credit Agreement borrowings | Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount				13,923,000
Credit Agreement borrowings | Third Amendment to the Credit Agreement | Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount				13,623,000
Mortgages
Line of Credit Facility [Line Items]
Total borrowings				28,223,000		28,963,000
Financing costs incurred	$ 1,064,000
Debt issuance cost amortization period (in years)	10 years
Debt instrument, periodic payment						750,000
Mortgages | Secured Debt
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 30,000,000			30,000,000
Mortgages | LIBOR
Line of Credit Facility [Line Items]
Interest rate (as a percent)	4.625%
Mortgages | Base Rate
Line of Credit Facility [Line Items]
Interest rate (as a percent)	3.625%
R&D Loan
Line of Credit Facility [Line Items]
Total borrowings				2,118,000		2,219,000
Loans payable				3,000,000
Interest-free loan
Line of Credit Facility [Line Items]
Total borrowings				877,000		$ 875,000
Loans payable				$ 1,000,000
Debt instrument, term (in years)				10 years