Company contributions vest at end of five years.

No definition available.

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- Definition

Company contributions vest at end of four years.

+ References

No definition available.

+ Details

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- Definition

Company contributions vest at end of three years.

+ References

No definition available.

+ Details

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- Definition

Company contributions vest at end of two year.

+ References

No definition available.

+ Details

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Namespace Prefix:	cgnx_
Data Type:	num:percentItemType
Balance Type:	na
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- Definition

Minimum age to be eligible to defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	cgnx_
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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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- Definition

Percentage employer matches of the employee's percentage contribution matched.

+ References

No definition available.

+ Details

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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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- Details

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Employee Savings Plan - Additional Information (Detail) - USD ($)	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2018	Oct. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Minimum age to be eligible to defined contribution plan			21 years
Maximum contribution by company expressed as percentage of employee pre-tax salary	10000.00%	50.00%
Company match percent			50.00%
Percent of employee contribution			6.00%
Company contributions vest at end of two years	25.00%	20.00%
Company contributions vest at end of three years	50.00%	40.00%
Company contributions vest at end of four years	75.00%	60.00%
Company contributions vest at end of five years	100.00%	100.00%
Company contributions to employee savings plan			$ 2,540,000	$ 2,030,000	$ 1,712,000
Highly Compensated Employee
Defined Contribution Plan Disclosure [Line Items]
Maximum contribution by company expressed as percentage of employee pre-tax salary			25.00%