Note 3 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	May 30, 2021	May 31, 2020	Mar. 01, 2020
Available-for-sale securities	$ 77,519	$ 77,519	$ 74,947
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities		77,519	74,947
Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
US Treasury and Government [Member]
Available-for-sale securities		60,395	56,906
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities		60,395	56,906
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Debt Security, Corporate, US [Member]
Available-for-sale securities		17,124	18,041
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities		17,124	18,041
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities