Note 3 - Marketable Securities - Summary of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	May. 31, 2015	Mar. 01, 2015
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	$ 135,577	$ 119,493
US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities (Note 3)	0	0
US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities (Note 3)	0	0
US Treasury and Government [Member]
Marketable securities (Note 3)	135,577	119,493
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	27,880	7,084
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities (Note 3)	4,002	4,018
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Marketable securities (Note 3)	0	0
Domestic Corporate Debt Securities [Member]
Marketable securities (Note 3)	31,882	11,102
Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	163,457	126,577
Fair Value, Inputs, Level 2 [Member]
Marketable securities (Note 3)	4,002	4,018
Fair Value, Inputs, Level 3 [Member]
Marketable securities (Note 3)	0	0
Marketable securities (Note 3)	$ 167,459	$ 130,595	[1]

[1] The balance sheet at March 1, 2015 has been derived from the audited financial statements at that date.