Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details) - USD ($) $ in Thousands |
Dec. 25, 2021 |
Dec. 26, 2020 |
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Amortized cost | $ 89,738 | $ 20,668 | ||||
Gross unrealized gains | 2 | 2 | ||||
Gross unrealized losses | [1] | 36 | 1 | |||
Short-term investments | 89,704 | 20,669 | ||||
Corporate Debt Securities [Member] | ||||||
Amortized cost | [2] | 84,060 | 14,943 | |||
Gross unrealized gains | [2] | 2 | 2 | |||
Gross unrealized losses | [1],[2] | 31 | 1 | |||
Short-term investments | [2] | 84,031 | 14,944 | |||
US Treasury Securities [Member] | ||||||
Amortized cost | 3,953 | 2,012 | ||||
Gross unrealized gains | 0 | 0 | ||||
Gross unrealized losses | [1] | 5 | 0 | |||
Short-term investments | 3,948 | 2,012 | ||||
Certificates of Deposit [Member] | ||||||
Amortized cost | 800 | 750 | ||||
Gross unrealized gains | 0 | 0 | ||||
Gross unrealized losses | [1] | 0 | 0 | |||
Short-term investments | 800 | 750 | ||||
US Government-sponsored Enterprises Debt Securities [Member] | ||||||
Amortized cost | 1,998 | |||||
Gross unrealized gains | 0 | |||||
Gross unrealized losses | [1] | 0 | ||||
Short-term investments | 1,998 | |||||
Debt Security, Government, Non-US [Member] | ||||||
Amortized cost | 925 | 965 | ||||
Gross unrealized gains | 0 | 0 | ||||
Gross unrealized losses | [1] | 0 | 0 | |||
Short-term investments | $ 925 | $ 965 | ||||
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