Note 3 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Nov. 27, 2022	Feb. 27, 2022
U.S. Treasury and other government securities	$ 98,693	$ 97,550
Fair Value, Inputs, Level 1 [Member]
U.S. Treasury and other government securities	98,693	97,550
Fair Value, Inputs, Level 2 [Member]
U.S. Treasury and other government securities	0	0
Fair Value, Inputs, Level 3 [Member]
U.S. Treasury and other government securities	0	0
US Treasury and Government [Member]
U.S. Treasury and other government securities	79,512	62,612
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
U.S. Treasury and other government securities	79,512	62,612
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
U.S. Treasury and other government securities	0	0
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
U.S. Treasury and other government securities	0	0
Debt Security, Corporate, US [Member]
U.S. Treasury and other government securities	19,181	34,938
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
U.S. Treasury and other government securities	19,181	34,938
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 2 [Member]
U.S. Treasury and other government securities	0	0
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 3 [Member]
U.S. Treasury and other government securities	$ 0	$ 0