Note 6 - Employee Benefit Plans - Benefit Obligation, Fair Value of Plan Assets, Funded Status and Liability of Swiss Plan (Details) - Swiss Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Benefit obligation at beginning of year	$ (30,512)	$ (27,499)
Service cost	(925)	(907)	$ (868)
Interest cost	(207)	(198)	(245)
Actuarial gain (loss)	708	(628)
Participant contributions	(816)	(789)
Benefits paid	1,079	743
Plan change	199
Foreign currency exchange adjustment	564	(1,234)
Benefit obligation at end of year	(29,910)	(30,512)	(27,499)
Fair value of plan assets at beginning of year	17,746	16,077
Return on assets, net of actuarial loss	114	112
Employer contributions	816	789
Participant contributions	816	789
Benefits paid	(1,079)	(743)
Foreign currency exchange adjustment	(325)	722
Fair value of plan assets at end of year	18,088	17,746	$ 16,077
Net liability at end of year	$ (11,822)	$ (12,766)