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. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Benefit obligation at beginning of year	$ 25,483	$ 26,027
Service cost	(868)	(856)	$ (749)
Interest cost	(245)	(311)	(491)
Actuarial loss	(796)	(660)
Participant contributions	(719)	(672)
Benefits paid	(214)	296
Plan change		558
Settlements		2,199
Foreign currency exchange adjustment	826	(10)
Benefit obligation at end of year	27,499	25,483	26,027
Fair value of plan assets at beginning of year	14,716	15,603
Return on assets, net of actuarial loss	189	277
Employer contributions	719	672
Participant contributions	719	672
Benefits paid	214	(296)
Settlements		(2,199)
Foreign currency exchange adjustment	(480)	(13)
Fair value of plan assets at end of year	16,077	14,716	$ 15,603
Net liability at end of year	$ (11,422)	$ (10,767)