Note 2 - Marketable Securities - Summary of Unrealized Gains and Losses on Available-for-sale Securities (Details) - USD ($) $ in Thousands	Feb. 26, 2023	Feb. 27, 2022
Amortized cost basis	$ 107,017	$ 100,241
Gross unrealized gains	0	10
Gross unrealized losses	5,814	2,701
US Treasury and Government [Member]
Amortized cost basis	89,603	65,177
Gross unrealized gains	0	5
Gross unrealized losses	5,744	2,570
Debt Security, Corporate, US [Member]
Amortized cost basis	17,414	35,064
Gross unrealized gains	0	5
Gross unrealized losses	$ 70	$ 131