Note 3 - Marketable Securities - Summary of Available-for-Sale Securities (Details) - USD ($)	Nov. 29, 2015	Mar. 01, 2015
US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	$ 125,146,000	$ 119,493,000
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)	125,146,000	119,493,000
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	27,762,000	7,084,000
Domestic Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Marketable securities (Note 3)	0	4,018,000
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)	27,762,000	11,102,000
Fair Value, Inputs, Level 1 [Member]
Marketable securities (Note 3)	152,908,000	126,577,000
Fair Value, Inputs, Level 2 [Member]
Marketable securities (Note 3)	0	4,018,000
Fair Value, Inputs, Level 3 [Member]
Marketable securities (Note 3)	0	0
Marketable securities (Note 3)	$ 152,908,000	$ 130,595,000	[1]

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