Note 2 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Feb. 26, 2023	Feb. 27, 2021
Available-for-sale securities	$ 101,203	$ 97,550
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	101,203	97,550
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	83,859	62,612
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	83,859	62,612
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	17,344	34,938
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	17,344	34,938
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