Note 2 - Goodwill and Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 25, 2021	Dec. 26, 2020
Beginning balance		$ 252,304	$ 238,669
Impact of currency exchange		(10,614)	13,635
Sale of PCB Test Business (1)	[1]	(21,899)
Ending balance		219,791	252,304
Semiconductor Test and Inspection [Member]
Beginning balance		230,724	218,775
Impact of currency exchange		(10,933)	11,949
Sale of PCB Test Business (1)	[1]	0
Ending balance		219,791	230,724
PCB Test [Member]
Beginning balance		21,580	19,894
Impact of currency exchange		319	1,686
Sale of PCB Test Business (1)	[1]	(21,899)
Ending balance		$ 0	$ 21,580

[1] On June 24, 2021, we completed the sale of our PCB Test business. See Note 14, “Business Divestitures and Discontinued Operations” for additional information.