Income Taxes - Narratives (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jan. 27, 2018	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015	Jul. 26, 2014
Income Tax Contingency [Line Items]
Tax Cuts and Jobs Act of 2017, adjustment to income tax liability	$ 32,200
Effective tax rate	33.00%
Cash tax benefit realized from option exercises and stock vestings	$ 7,800
Unrecognized tax benefits	3,322	$ 3,072	$ 2,440	$ 2,327	$ 2,401
Payment of interest and penalties accrued	1,200	1,200	1,000
Tax benefit from exercise of stock options	7,800
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount		6,000	4,500	4,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount		1,300	2,500	2,800
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	$ 1,596	0	0	0
Non deductible ana non taxable item
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount		$ 1,000	$ 700	$ 500