Note 2 - Marketable Securities - Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Feb. 26, 2017	Feb. 28, 2016
Marketable securities	$ 136,152	$ 139,668
Fair Value, Inputs, Level 1 [Member]
Marketable securities	136,152	139,668
Fair Value, Inputs, Level 2 [Member]
Marketable securities
Fair Value, Inputs, Level 3 [Member]
Marketable securities
US Treasury and Government [Member]
Marketable securities	111,261	118,194
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities	111,261	118,194
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities
Domestic Corporate Debt Securities [Member]
Marketable securities	24,891	21,474
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities	24,891	21,474
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities