Goodwill and Acquired Intangibles (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Jan. 03, 2015	Dec. 28, 2013	Dec. 29, 2012
Amortization of acquired intangibles
Cost of product and maintenance	$ 36,907	$ 24,023	$ 13,541
Amortization of acquired intangibles	24,017us-gaap_AmortizationOfIntangibleAssets	19,416us-gaap_AmortizationOfIntangibleAssets	15,077us-gaap_AmortizationOfIntangibleAssets
Total amortization of acquired intangibles	$ 60,924cdns_AmortizationOfAcquiredIntangibles	$ 43,439cdns_AmortizationOfAcquiredIntangibles	$ 28,618cdns_AmortizationOfAcquiredIntangibles

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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

-Publisher FASB

-Name Accounting Standards Codification

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-Section 45

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Topic 350

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