Segment and Geographic Information - Information About the Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Product revenue	$ 451,066us-gaap_SalesRevenueGoodsNet	$ 326,786us-gaap_SalesRevenueGoodsNet	$ 295,588us-gaap_SalesRevenueGoodsNet
Service revenue	35,204us-gaap_SalesRevenueServicesNet	27,100us-gaap_SalesRevenueServicesNet	28,691us-gaap_SalesRevenueServicesNet
Depreciation and amortization	12,467us-gaap_DepreciationAndAmortization	11,102us-gaap_DepreciationAndAmortization	10,858us-gaap_DepreciationAndAmortization
Goodwill and intangibles	92,388cgnx_GoodwillAndIntangibleAssets	96,412cgnx_GoodwillAndIntangibleAssets	96,459cgnx_GoodwillAndIntangibleAssets
Operating income	143,663us-gaap_OperatingIncomeLoss	86,368us-gaap_OperatingIncomeLoss	83,407us-gaap_OperatingIncomeLoss
MVSD [Member]
Segment Reporting Information [Line Items]
Product revenue	409,017	298,186	263,308
Service revenue	17,432	9,465	10,388
Depreciation and amortization	10,580	9,569	9,505
Goodwill and intangibles	87,059	90,718	90,390
Operating income	156,552	99,383	89,378
SISD [Member]
Segment Reporting Information [Line Items]
Product revenue	42,049	28,600	32,280
Service revenue	17,772	17,635	18,303
Depreciation and amortization	1,138	1,078	963
Goodwill and intangibles	5,329	5,694	6,069
Operating income	15,598	8,990	11,941
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	749	455	390
Operating income	$ (28,487)	$ (22,005)	$ (17,912)

Goodwill and intangible assets.

No definition available.

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- Definition

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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- Definition

Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(a))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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- Definition

Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(d))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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