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Balance Sheet Components - Marketable Securities (Details) - USD ($) $ in Thousands | Dec. 26, 2020 | Dec. 28, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | $ 67,493 | $ 76,231
Gross Unrealized Gains | 319 | 123
Gross Unrealized Losses | (2) | (27)
Fair Value | 67,810 | 76,327
Amortized Cost |  |
Due in one year or less | 50,500 | 38,899
Due after one year to five years | 16,993 | 37,332
Amortized Cost | 67,493 | 76,231
Fair Value |  |
Due in one year or less | 50,679 | 38,944
Due after one year to five years | 17,131 | 37,383
Fair Value | 67,810 | 76,327
U.S. Treasuries |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 40,602 | 10,458
Gross Unrealized Gains | 124 | 11
Gross Unrealized Losses | 0 | 0
Fair Value | 40,726 | 10,469
Amortized Cost |  |
Amortized Cost | 40,602 | 10,458
Fair Value |  |
Fair Value | 40,726 | 10,469
Commercial paper |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost |  | 3,914
Gross Unrealized Gains |  | 1
Gross Unrealized Losses |  | (4)
Fair Value |  | 3,911
Amortized Cost |  |
Amortized Cost |  | 3,914
Fair Value |  |
Fair Value |  | 3,911
Corporate bonds |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 24,156 | 33,867
Gross Unrealized Gains | 176 | 68
Gross Unrealized Losses | (2) | (7)
Fair Value | 24,330 | 33,928
Amortized Cost |  |
Amortized Cost | 24,156 | 33,867
Fair Value |  |
Fair Value | 24,330 | 33,928
Certificates of deposit |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 2,160 | 3,584
Gross Unrealized Gains | 19 | 5
Gross Unrealized Losses | 0 | 0
Fair Value | 2,179 | 3,589
Amortized Cost |  |
Amortized Cost | 2,160 | 3,584
Fair Value |  |
Fair Value | 2,179 | 3,589
Agency securities |  |
Debt Securities, Available-for-sale [Abstract] |  |
Amortized Cost | 575 | 24,408
Gross Unrealized Gains | 0 | 38
Gross Unrealized Losses | 0 | (16)
Fair Value | 575 | 24,430
Amortized Cost |  |
Amortized Cost | 575 | 24,408
Fair Value |  |
Fair Value | $ 575 | $ 24,430

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