Note 9 - Facility Sale (Details Textual) $ in Millions	Sep. 21, 2015 USD ($)
Poway Facility [Member]
Disposal Group, Not Discontinued Operation, Consideration	$ 34.3

Potential future selling price of facility currently in escrow.

No definition available.

Name:	cohu_DisposalGroupNotDiscontinuedOperationConsideration
Namespace Prefix:	cohu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant