Note 8 - Employee Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Nora Defined Benefit Plan [Member]
Service cost	$ 134		$ 134
Interest cost	99		99
Net periodic benefit cost	233		233
Service cost	134		134
Interest cost	99		99
Foreign Plan [Member]
Service cost	178	$ 423	547	$ 1,204
Interest cost	1,270	1,426	3,941	4,138
Expected return on assets	(1,503)	(1,697)	(4,667)	(4,920)
Amortization of prior service costs	(11)	9	4	26
Recognized net actuarial (gains) / losses	270	318	839	930
Net periodic benefit cost	204	479	664	1,378
Service cost	178	423	547	1,204
Interest cost	1,270	1,426	3,941	4,138
UNITED STATES | Salary Continuation Plan [Member]
Service cost	0	0	0	0
Interest cost	271	314	812	942
Amortization of prior service costs	0	0	0	0
Net periodic benefit cost	387	405	1,160	1,215
Amortization of (gain) / loss	116	91	348	273
Service cost	0	0	0	0
Interest cost	$ 271	$ 314	$ 812	$ 942