Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 30, 2019	Mar. 31, 2018
Net sales	[1]	$ 147,809	$ 95,150
Semiconductor Test and Inspection [Member]
Net sales		136,694	95,150
PCB Test [Member]
Net sales		11,115
Systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	[1]	79,940	54,905
Systems [Member] | PCB Test [Member]
Net sales	[1]	6,972
Non-systems [Member] | Semiconductor Test and Inspection [Member]
Net sales	[1]	56,753	40,245
Non-systems [Member] | PCB Test [Member]
Net sales	[1]	4,144
CHINA
Net sales		23,551	20,243
UNITED STATES
Net sales		17,101	14,478
Malaysia [Member]
Net sales		17,714	11,809
TAIWAN, PROVINCE OF CHINA
Net sales		14,970	2,941
PHILIPPINES
Net sales		14,541	10,546
Rest of the World [Member]
Net sales		$ 59,932	$ 35,133

[1] After the acquisition of Xcerra on October 1, 2018 we report in two segments, Semiconductor Test & Inspection and PCB Test. Cohu's historical reported net sales would have been reported in our Semiconductor Test & Inspection segment and have been presented accordingly.