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Stock Based Compensation (Details Textual) (Stock option and restricted stock grants [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended
Apr. 04, 2015
Stock option and restricted stock grants [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Total unrecognized compensation expense, net of forfeitures $ 129.8us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= cdns_StockoptionandrestrictedstockgrantsMember
Weighted-average vesting period over which unrecognized compensation expense will be recognized 2 years