Note 2 - Business Acquisitions - Purchase Price Allocation, Xcerra Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended	14 Months Ended
		Dec. 28, 2019	Dec. 28, 2019	Dec. 29, 2018	Oct. 01, 2018	Dec. 30, 2017
Goodwill		$ 238,669	$ 238,669	$ 242,127		$ 65,613
Goodwill, measurement period adjustments		1,134
Xcerra [Member]
Current assets, including cash received		375,990	375,990		$ 375,990
Property, plant and equipment		40,729	40,729		40,729
Other assets		1,051	1,051		2,109
Other assets, measurement period adjustments	[1]		(1,058)
Intangible assets		321,160	321,160		321,160
Goodwill		180,397	180,397		179,263
Goodwill, measurement period adjustments	[1]		1,134
Total assets acquired		919,327	919,327		919,251
Liabilities assumed		(124,897)	(124,897)		(124,821)
Liabilities assumed, measurement period adjustments	[1]		(76)
Net assets acquired		$ 794,430	$ 794,430		$ 794,430

[1] Measurement period adjustments made as a result of obtaining new facts and circumstances related to certain assets acquired and liabilities assumed as of the date of acquisition. The net impact of the measurement period adjustments were offset against goodwill.