XML 75 R41.htm IDEA: XBRL DOCUMENT v2.4.1.9
Cash, Cash Equivalents, and Investments - Additional Information (Detail) (USD $)
 3 Months Ended
Apr. 05, 2015
Mar. 30, 2014
Amortized Cost And Fair Value Debt Securities [Abstract]    
Gross realized gains on sale of investments $ 197,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains $ 512,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Gross realized losses on sale of investments 168,000us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses 11,000us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses
Maximum amount committed to invest in limited partnership 20,500,000cgnx_MaximumInvestmentInLimitedPartnership  
Contribution to limited partnership 19,886,000cgnx_ContributionToLimitedPartnership  
Remaining amount of commitment in limited partnership 614,000cgnx_RemainingAmountOfCommitment  
Investment expiration date Dec. 31, 2015  
Number of contributions made during the period 0cgnx_ContributionMadeToPartnershipDuringPeriod  
Distributions From Partnership During Period $ 0cgnx_DistributionsFromPartnershipDuringPeriod