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Stock Repurchase Program - Additional Information (Detail) (Common Stock, USD $)
Nov. 30, 2008
Apr. 29, 2014
Repurchase Program 2011
    
Equity [Line Items]    
Repurchase of authorized common stock $ 80,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cgnx_RepurchaseProgram2011Member
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember		  
Repurchase Program 2014
    
Equity [Line Items]    
Repurchase of authorized common stock   $ 50,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cgnx_RepurchaseProgram2014Member
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonStockMember