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Income Taxes - Narratives (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jan. 27, 2018 | Jan. 26, 2019 | Jul. 29, 2017 | Jul. 30, 2016 | Jul. 25, 2015
Income Tax Contingency [Line Items] |  |  |  |  |
Tax Cuts and Jobs Act of 2017, adjustment to income tax liability | $ 32,200 |  |  |  |
Effective tax rate | 33.00% |  |  |  |
Unrecognized tax benefits | $ 3,322 | $ 3,786 | $ 3,072 | $ 2,440 | $ 2,327
Payment of interest and penalties accrued | 1,200 | 1,400 |  |  |
Tax benefit from exercise of stock options | 7,800 |  |  |  |
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount |  |  | 6,000 | 4,500 |
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount |  |  | 1,300 | 2,500 |
Effective Income Tax Rate Reconciliation, Tax Credit, Amount | $ 1,596 | $ 1,835 | 0 | 0 |
Non deductible ana non taxable item |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |
Effective Income Tax Rate Reconciliation, Tax Credit, Amount |  |  | $ 1,000 | $ 700 |

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