Note 2 - Business Acquisitions, Goodwill and Purchased Intangible Assets - Purchase Price Allocation, Xcerra Acquisition (Details) - USD ($) $ in Thousands		Jun. 29, 2019	Dec. 29, 2018	[1]	Oct. 01, 2018	Dec. 30, 2017
Goodwill		$ 241,466	$ 242,127			$ 65,613
Xcerra [Member]
Current assets, including cash received					$ 375,990
Property, plant and equipment					40,729
Other assets	[2]				1,051
Intangible assets					321,160
Goodwill	[2]				179,961
Total assets acquired					918,891
Liabilities assumed	[2]				(124,461)
Net assets acquired					$ 794,430

[1] Derived from December 29, 2018 audited financial statements

[2] Includes a measurement period adjustment recorded during the three months ended June 29, 2019, as a result of obtaining new facts and circumstances related to certain assets acquired ($1.1 million) and liabilities assumed ($0.4 million) as of the date of acquisition. The net impact of this measurement period adjustment, totaling $0.7 million, was offset against goodwill.