Note 9 - Employee Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Nora Defined Benefit Plan [Member]
Service cost	$ 216		$ 433
Interest cost	171		345
Net periodic benefit cost	387		778
Foreign Plan [Member]
Service cost	184	$ 182	369	$ 369
Interest cost	1,266	1,318	2,547	2,671
Expected return on assets	(1,428)	(1,562)	(2,873)	(3,164)
Amortization of prior service cost	16	8	32	15
Amortization of net actuarial losses	249	281	502	569
Net periodic benefit cost	287	227	577	460
Amortization of net actuarial losses	249	281	502	569
UNITED STATES | Salary Continuation Plan [Member]
Service cost	0	0	0	0
Interest cost	289	271	577	541
Amortization of prior service cost	0	0	0	0
Amortization of net actuarial losses	93	116	187	232
Net periodic benefit cost	382	387	764	773
Amortization of net actuarial losses	$ 93	$ 116	$ 187	$ 232