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Fair Value Measurements - Assets and Liabilities Carried at Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands | Mar. 27, 2021 | Dec. 26, 2020
--- | --- | ---
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | $ 266,450 | $ 237,002
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Total assets | 266,450 | 237,002
Foreign currency forward contracts | 229 | 36
Total liabilities | 229 | 36
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] | Municipal notes and bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 136,538 | 124,640
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 9,180 | 11,708
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 36,472 | 36,373
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 51,789 | 32,699
Carrying Value [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 32,471 | 31,582
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Total assets | 0 | 0
Foreign currency forward contracts | 0 | 0
Total liabilities | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Municipal notes and bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Total assets | 266,450 | 237,002
Foreign currency forward contracts | 229 | 36
Total liabilities | 229 | 36
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Municipal notes and bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 136,538 | 124,640
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 9,180 | 11,708
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 36,472 | 36,373
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 51,789 | 32,699
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 32,471 | 31,582
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Total assets | 0 | 0
Foreign currency forward contracts | 0 | 0
Total liabilities | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Municipal notes and bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Commercial paper [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Corporate bonds [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Available-for-sale debt securities | $ 0 | $ 0

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