Note 6 - Employee Benefit Plans - Net Periodic Benefit Cost of Swiss Plan (Details) - Swiss Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Service cost	$ 920	$ 925	$ 907
Interest cost	267	207	198
Expected return on assets	(168)	(124)	(119)
Net periodic costs	$ 1,019	$ 1,008	$ 986