Note 5 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 24, 2022	Dec. 25, 2021
Due in one year or less	$ 112,027	$ 83,429
Due in one year or less, fair value	111,625	83,408
Due after one year through three years	25,859	6,309
Due after one year through three years, fair value	25,358	6,296
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Total	137,886	89,738
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value, Total	$ 136,983	$ 89,704