Note 10 - Segment and Geographic Information - Summary of Current Segments (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020	Dec. 26, 2020
Net sales		$ 244,803	$ 144,084	$ 470,291	$ 283,005
Profit (loss) for reportable segments		42,079	(320)	81,135	(10,899)
Gain (Loss) on Disposition of Business	[1]	75,779	(0)	75,664	(0)
Interest expense		(1,831)	(3,456)	(4,406)	(7,883)
Interest income		94	21	144	168
Gain (Loss) on Extinguishment of Debt, Total		0	0	(1,761)	0
Income (loss) from continuing operations before taxes		112,755	(4,603)	143,937	(22,913)
Total assets for reportable segments		1,371,732		1,371,732		$ 1,090,346	[2]
Corporate, Non-Segment [Member]
Corporate expenses		(3,366)	(848)	(6,839)	(4,299)
Total assets for reportable segments		191,727		191,727		55,492
Semiconductor Test and Inspection [Member]
Net sales		231,125	131,428	443,531	259,441
Profit (loss) for reportable segments		40,601	(2,331)	77,228	(13,904)
Total assets for reportable segments		1,180,005		1,180,005		968,028
PCB Test [Member]
Net sales		13,678	12,656	26,760	23,564
Profit (loss) for reportable segments		1,478	$ 2,011	3,907	$ 3,005
Total assets for reportable segments		0		0		66,826
Semiconductor Test and Inspection and PCB Test [Member]
Total assets for reportable segments		$ 1,180,005		$ 1,180,005		$ 1,034,854

[1] On June 24, 2021 we completed the divestment of our PCB Test business. The divestment of this business did not qualify for presentation as discontinued operations and the results of the PCB Test business are included in continuing operations for all periods presented. See Note 12, “Business Divestiture and Discontinued Operations” for additional information on this transaction and financial statement presentation.

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