Note 3 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	May 28, 2017	Feb. 26, 2017
Available-for-sale Securities	$ 190,487	$ 136,152
Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	190,487	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	152,280	111,261
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	152,280	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	38,207	24,891
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	38,207	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