Industry Segments - Schedule of Customer Concentration to Consolidated Net Sales (Detail)	3 Months Ended	9 Months Ended
Sep. 28, 2013 Customer	Sep. 29, 2012 Customer	Sep. 28, 2013 Customer	Sep. 29, 2012 Customer
Segment Reporting [Abstract]
Customers individually accounting for more than 10% of consolidated net sales	1	1	1	1
Percentage of consolidated net sales	17.00%	39.00%	18.00%	41.00%

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