Note 3 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 01, 2019	Mar. 03, 2019
Available-for-sale securities	$ 120,124	$ 80,617
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	120,124	80,617
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	97,064	68,718
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	97,064	68,718
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	23,060	11,899
Debt Security, Corporate, US [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	23,060	11,899
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