Note 4 - Financial Instruments Measured at Fair Value - Short-Term Investments by Security Type (Details) - USD ($) $ in Thousands	Jun. 27, 2015	Dec. 27, 2014
Foreign Government Debt Securities [Member]
Investments, amortized cost	$ 453
Short-term investments	453
Municipal Bonds [Member]
Investments, amortized cost		$ 155
Short-term investments		155
Certificates of Deposit [Member]
Investments, amortized cost	1,000	1,000
Short-term investments	1,000	1,000
Investments, amortized cost	1,453	1,155
Short-term investments	$ 1,453	$ 1,155