Long-Term Debt and Credit Arrangements - Narrative (Details)		3 Months Ended		12 Months Ended
	Apr. 28, 2017 USD ($)	Jul. 28, 2017 USD ($)	Jul. 29, 2016	Apr. 28, 2017 USD ($)
Line of Credit Facility [Line Items]
Total borrowings	$ 2,695,000	$ 92,593,000		$ 2,695,000
Amortization of debt issuance costs	1,542,000
Effective interest rate		2.71%	2.48%
Revolving Credit Facility | Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	300,000,000			$ 300,000,000
Debt instrument, term (in years)				5 years
Line of credit facility, borrowing increase	$ 400,000,000			$ 400,000,000
Coverage ratio requirement (not less than)	3.00			3.00
Leverage ratio requirement (not to exceed)	3.50			3.50
Revolving Credit Facility | Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee (as a percent)				0.20%
Revolving Credit Facility | Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee (as a percent)				0.30%
Revolving Credit Facility | Credit Facility | Eurodollar
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				1.00%
Revolving Credit Facility | Credit Facility | Eurodollar | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				1.25%
Revolving Credit Facility | Credit Facility | Eurodollar | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				2.00%
Revolving Credit Facility | Credit Facility | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				0.50%
Revolving Credit Facility | Credit Facility | Base Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				0.25%
Revolving Credit Facility | Credit Facility | Base Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				1.00%
Revolving Credit Facility | Credit Facility | Federal Funds Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				0.50%
Revolving Credit Facility | Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (as a percent)				1.50%
Standby Letters of Credit | Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 20,000,000			$ 20,000,000
Credit Agreement borrowings
Line of Credit Facility [Line Items]
Total borrowings	0	$ 90,000,000		0
Revolving credit facility, maximum borrowing capacity		300,000,000
Credit Agreement borrowings | Standby Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount		7,136,000
R&D Loan
Line of Credit Facility [Line Items]
Total borrowings	1,801,000	1,695,000		1,801,000
Loans payable		3,000,000
Interest-free loan
Line of Credit Facility [Line Items]
Total borrowings	$ 894,000	898,000		$ 894,000
Loans payable		$ 1,000,000
Debt instrument, term (in years)		10 years