Note 3 - Marketable Securities - Summary of Unrealized Gains and Losses on Available-for-sale Securities (Details) - USD ($) $ in Thousands	Aug. 26, 2018	Feb. 25, 2018
Amortized cost basis	$ 89,128	$ 91,791
Gross unrealized gains
Gross unrealized losses	1,672	1,814
US Treasury and Government [Member]
Amortized cost basis	78,086	80,116
Gross unrealized gains
Gross unrealized losses	1,644	1,755
Debt Security, Corporate, US [Member]
Amortized cost basis	11,042	11,675
Gross unrealized gains
Gross unrealized losses	$ 28	$ 59