Note 2 - Goodwill and Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 24, 2022		Dec. 25, 2021
Beginning balance		$ 219,791	[1]	$ 252,304
Sale of PCB Test Business (1)	[2]			(21,899)
Impact of currency exchange		(17,077)		(10,614)
Ending balance		202,714		219,791	[1]
Semiconductor Test and Inspection [Member]
Beginning balance		219,791		230,724
Sale of PCB Test Business (1)	[2]			0
Impact of currency exchange		(17,077)		(10,933)
Ending balance		202,714		219,791
PCB Test [Member]
Beginning balance		0		21,580
Sale of PCB Test Business (1)	[2]			(21,899)
Impact of currency exchange		0		319
Ending balance		$ 0		$ 0

[1] Derived from December 25, 2021 audited financial statements

[2] On June 24, 2021, we completed the sale of our PCB Test business. See Note 12, “Business Divestitures” for additional information.