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Schedule II - Valuation and Qualifying Accounts - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 27, 2025	Dec. 28, 2024	Dec. 30, 2023
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
Balance, beginning of year		$ 190	$ 340	$ 199
Additions (reductions) not charged to expense	[1]	11	(14)	5
Additions (reduction) charged (credited) to expense		(69)	15	140
Deductions/write-offs		42	151	4
Balance, end of year		90	190	340
SEC Schedule, 12-09, Reserve, Inventory [Member]
Balance, beginning of year		28,177	20,418	26,871
Additions (reductions) not charged to expense		210	6,203	648
Additions (reduction) charged (credited) to expense		7,466	5,442	4,540
Deductions/write-offs		7,229	3,886	11,641
Balance, end of year		$ 28,624	$ 28,177	$ 20,418
[1] (1) Changes in reserve balances resulting from foreign currency impact and reclassifications from other reserves.

X

- Definition

Amount of increase (decrease) in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges (credits) to costs and expenses.

+ References

No definition available.

+ Details

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Balance Type:	credit
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X

- Definition

Amount of increase (decrease) in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, not charged (credited) to costs and expenses.

+ References

No definition available.

+ Details

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X

- Definition

Amount of decrease (increase) in valuation and qualifying accounts and reserves.

+ References

No definition available.

+ Details

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Namespace Prefix:	cohu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column E))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4

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X

- Details

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