Industry Segments - Schedule of Customer Concentration to Consolidated Net Sales (Detail)	3 Months Ended	6 Months Ended
Jun. 28, 2014 Customer	Jun. 29, 2013 Customer	Jun. 28, 2014 Customer	Jun. 29, 2013 Customer
Segment Reporting [Abstract]
Customers individually more than 10% of consolidated net sales	3	2	3	1
Percentage of consolidated net sales	38.00%	29.00%	37.00%	19.00%

Percentage of consolidated net sales attributable to significant customer.

No definition available.

Name:	cohu_PercentageOfConsolidatedNetSalesAttributableToSignificantCustomer
Namespace Prefix:	cohu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration