Debt - Narrative (Details)			3 Months Ended			6 Months Ended
	Oct. 21, 2015 USD ($)	Jan. 02, 2014 USD ($)	Oct. 23, 2015 USD ($)	Jul. 24, 2015 USD ($)	Oct. 24, 2014	Oct. 23, 2015 USD ($)	Oct. 24, 2014	Apr. 24, 2015 USD ($)	Jul. 23, 2014 USD ($)
Line of Credit Facility [Line Items]
Total borrowings			$ 474,668,000			$ 474,668,000		$ 451,085,000
Financing costs		$ 2,064,000		$ 1,705,000
Revolving credit facility (up to)	$ 650,000,000
Line of credit facility, amount outstanding	50,000,000
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%
Revolving credit facility, maximum borrowing capacity		$ 750,000,000
Debt instrument, fee amount	$ 812,000
Write off of deferred debt issuance cost	480,000
Additional indebtedness allowed (up to)	$ 300,000,000
Effective interest rate			1.97%		2.06%	2.09%	1.84%
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%
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			3.00
Leverage ratio requirement (not to exceed)			4.50			4.50
Current coverage ratio			12.08			12.08
Current leverage ratio			3.12			3.12
Additional indebtedness allowed (up to)	300,000,000
Credit agreement, additional capacity, mortgage indebtedness (up to)	50,000,000
Third Amendment to the Credit Agreement | Credit Agreement borrowings
Line of Credit Facility [Line Items]
Credit agreement, sale leaseback capacity	$ 300,000
Credit Agreement borrowings
Line of Credit Facility [Line Items]
Total borrowings			$ 471,377,000			$ 471,377,000		447,599,000
Credit Agreement borrowings | Standby Letters of Credit
Line of Credit Facility [Line Items]
Line of credit facility, amount outstanding			12,117,000			12,117,000
Letters of credit outstanding, amount			12,418,000			12,418,000
R&D Loan
Line of Credit Facility [Line Items]
Total borrowings			2,426,000			2,426,000		2,631,000
Loans payable			3,000,000			3,000,000
Interest-free loan
Line of Credit Facility [Line Items]
Total borrowings			865,000			865,000		$ 855,000
Loans payable			1,000,000			$ 1,000,000
Debt instrument, term						10 years
OHIO | R&D Loan
Line of Credit Facility [Line Items]
Total borrowings			$ 2,426,000			$ 2,426,000