Note 5 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details) $ in Thousands	Dec. 25, 2021 USD ($)
Due in one year or less, amortized cost	$ 83,429
Due in one year or less, fair value	83,408
Due after one year through three years, amortized cost	6,309
Due after one year through three years, fair value	6,296
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Total	89,738
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value, Total	$ 89,704