Note 9 - Income Taxes - Reconciliation of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Balance at beginning of year	$ 34,740	$ 34,873	$ 10,321
Additions for tax positions of current year	817	1,231	524
Additions (reductions) for tax positions of prior years	(425)	(484)
Additions (reductions) for tax positions of prior years			191
Reductions due to lapse of the statute of limitations	(304)	(957)	(645)
Additions related to Xcerra acquisition	0	0	24,524
Reductions due to settlements	(1,134)	(30)	0
Foreign exchange rate impact	2	107
Foreign exchange rate impact			(42)
Balance at end of year	$ 33,696	$ 34,740	$ 34,873