Note 3 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Nov. 26, 2017	Feb. 26, 2017
Available-for-sale securities	$ 201,233	$ 136,152
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	201,233	136,152
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	158,276	111,261
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	158,276	111,261
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
Domestic Corporate Debt Securities [Member]
Available-for-sale securities	42,957	24,891
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	42,957	24,891
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities