Note 10 - Segment and Geographic Information - Summary of Current Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2021	Mar. 28, 2020	Dec. 26, 2020
Net sales	$ 225,488	$ 138,921
Profit (loss) for reportable segments	39,056	(10,579)
Interest expense	(2,575)	(4,427)
Interest income	50	147
Gain (Loss) on Extinguishment of Debt, Total	(1,761)	0
Income (loss) from continuing operations before taxes	31,182	(18,310)
Total assets for reportable segments	1,258,755		$ 1,090,346	[1]
Corporate, Non-Segment [Member]
Corporate expenses	(3,588)	(3,451)
Total assets for reportable segments	179,594		55,492
Semiconductor Test and Inspection [Member]
Net sales	212,406	128,013
Profit (loss) for reportable segments	36,627	(11,573)
Total assets for reportable segments	1,012,182		968,028
PCB Test [Member]
Net sales	13,082	10,908
Profit (loss) for reportable segments	2,429	$ 994
Total assets for reportable segments	66,979		66,826
Semiconductor Test and Inspection and PCB Test [Member]
Total assets for reportable segments	$ 1,079,161		$ 1,034,854

[1] Derived from December 26, 2020 audited financial statements