Note 6 - Restructuring - Activity Related to Restructuring Plans (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Accrued Restructuring				$ 7,610	$ 10,680
Restructuring charges		$ 2,692	$ 252	4,178	4,719
Costs paid or otherwise settled				(3,055)	(6,307)
Accrued Restructuring		8,733	9,092	8,733	9,092
Employee Severance [Member]
Accrued Restructuring	[1]			160	1,814
Restructuring charges	[1]			1,733	625
Costs paid or otherwise settled	[1]			(1,254)	(2,279)
Accrued Restructuring	[1]	639	160	639	160
Lease Termination and Fixed Assets [Member]
Accrued Restructuring				6,585	8,630
Restructuring charges				2,132	2,482
Costs paid or otherwise settled				(1,275)	(3,714)
Accrued Restructuring		7,442	7,398	7,442	7,398
Software Contracts and Engineering Tools [Member]
Accrued Restructuring	[2]			0	218
Restructuring charges	[2]			0	0
Costs paid or otherwise settled	[2]			0	(218)
Accrued Restructuring	[2]	0	0	0	0
Other Restructuring [Member]
Accrued Restructuring	[3]			865	18
Restructuring charges	[3]			313	1,612
Costs paid or otherwise settled	[3]			(526)	(96)
Accrued Restructuring	[3]	$ 652	$ 1,534	$ 652	$ 1,534

[1] Includes employee relocation and outplacement costs

[2] Includes cancellation of contracts, asset impairments, and accelerated depreciation on certain enterprise resource planning and customer relationship management systems

[3] Beginning in the second quarter of fiscal 2019, "Other" included termination fees on the cancellation of certain contracts under the Q2 2019 Sales Plan