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Goodwill and Intangible Assets - Narrative (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Jul. 28, 2013
Jan. 25, 2015
Jan. 26, 2014
Jan. 27, 2013
Goodwill and Intangible Assets [Line Items]        
Goodwill impairment   $ 0us-gaap_GoodwillImpairmentLoss $ 116,686us-gaap_GoodwillImpairmentLoss $ 0us-gaap_GoodwillImpairmentLoss
Impairment of indefinite-lived intangible assets $ 2,600us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill      
In-process research and development | Income approach        
Goodwill and Intangible Assets [Line Items]        
Discount rate used to value IPR&D   12.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InProcessResearchAndDevelopmentMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_IncomeApproachValuationTechniqueMember
12.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InProcessResearchAndDevelopmentMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_IncomeApproachValuationTechniqueMember
 
Market participant tax rate used to value IPR&D   28.10%smtc_FairValueInputsTaxRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InProcessResearchAndDevelopmentMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_IncomeApproachValuationTechniqueMember
19.00%smtc_FairValueInputsTaxRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InProcessResearchAndDevelopmentMember
/ us-gaap_ValuationTechniqueAxis
= us-gaap_IncomeApproachValuationTechniqueMember