Note 2 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Feb. 27, 2022	Feb. 28, 2021
Available-for-sale securities	$ 97,550	$ 74,947
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	97,550	74,947
Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0	0
US Treasury and Government [Member]
Available-for-sale securities	62,612	56,906
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	62,612	56,906
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	0	0
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0	0
Debt Security, Corporate, US [Member]
Available-for-sale securities	34,938	18,041
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	34,938	18,041
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	0	0
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	$ 0	$ 0