Employee service share based compensation recognized period costs capitalized amount.

No definition available.

Name:	cgnx_EmployeeServiceShareBasedCompensationRecognizedPeriodCostsCapitalizedAmount
Namespace Prefix:	cgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Estimated forfeiture rate for unvested options for all non-senior management.

+ References

No definition available.

+ Details

Name:	cgnx_EstimatedForfeitureRateForUnvestedOptionsForAllNonSeniorManagement
Namespace Prefix:	cgnx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Estimated forfeiture rate for unvested options for senior management.

+ References

No definition available.

+ Details

Name:	cgnx_EstimatedForfeitureRateForUnvestedOptionsForSeniorManagement
Namespace Prefix:	cgnx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Expiration period of stock option plan.

+ References

No definition available.

+ Details

Name:	cgnx_ExpirationPeriodOfStockOptionPlan
Namespace Prefix:	cgnx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase (decrease) in compensation expense due to revised estimated forfeiture rates.

+ References

No definition available.

+ Details

Name:	cgnx_IncreaseInCompensationExpenseDueToRevisedEstimatedForfeitureRates
Namespace Prefix:	cgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of groups within employee population.

+ References

No definition available.

+ Details

Name:	cgnx_NumberOfGroupsWithinEmployeePopulation
Namespace Prefix:	cgnx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of stock options granted to all other employees expected to vest.

+ References

No definition available.

+ Details

Name:	cgnx_PercentageOfStockOptionsGrantedToAllOtherEmployeesExpectedToVest
Namespace Prefix:	cgnx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of stock options granted to senior management expected to vest.

+ References

No definition available.

+ Details

Name:	cgnx_PercentageOfStockOptionsGrantedToSeniorManagementExpectedToVest
Namespace Prefix:	cgnx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share based compensation arrangement by share based payment award options vested fair value.

+ References

No definition available.

+ Details

Name:	cgnx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedFairValue
Namespace Prefix:	cgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Shares based compensation arrangement by shares based payment award options exercisable intrinsic value.

+ References

No definition available.

+ Details

Name:	cgnx_SharesBasedCompensationArrangementBySharesBasedPaymentAwardOptionsExercisableIntrinsicValue
Namespace Prefix:	cgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

No definition available.

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsDisposedOfBySaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stock-Based Compensation Expense - Additional Information (Detail)		12 Months Ended
	Jul. 06, 2015 USD ($) shares	Dec. 31, 2016 USD ($) Employees $ / shares shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of groups within the employee population \| Employees		2
Percentage of stock options granted to all other employees expected to vest		72.00%
Percentage of stock options granted to senior management expected to vest		77.00%
Estimated forfeiture rate for unvested options for senior management		9.00%
Estimated forfeiture rate for unvested options for all non-senior management		11.00%
Increase In Compensation Expense Due To Revised Estimated Forfeiture Rates		$ 334,000	$ 461,000	$ 288,000
Weighted-average grant-date fair values of stock options granted \| $ / shares		$ 12.65	$ 14.35	$ 15.97
Total intrinsic values of stock options exercised		$ 55,580,000	$ 43,987,000	$ 31,884,000
Total fair values of stock options vested		18,114,000	16,227,000	11,627,000
Total unrecognized compensation expense related to non-vested stock options		$ 19,742,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Period for Recognition		1 year 6 months 7 days
Stock-based compensation expense		$ 20,558,000	21,274,000	15,158,000
Income tax benefit recognized related to stock-based compensation expense		6,747,000	7,127,000	4,977,000
Compensation expense capitalized		$ 0	$ 0	$ 0
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under stock option plans \| shares		8,078,751
Vesting period for stock option plans		4 years
Expiration period of stock option plan		10 years
Discontinued Operations, Disposed of by Sale [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,106,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number \| shares	190,000