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Fair Value of Financial Instruments (Details 2) (Auction rate securities, Weighted Average, Discounted cash flow)
 3 Months Ended
Apr. 04, 2015
Auction rate securities | Weighted Average | Discounted cash flow
  
Quantitative information for Level 3 Fair Value Measurements Assets  
Estimated yield (as a percent) 0.97%slab_FairValueInputsEstimatedInterestRates
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_AuctionRateSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= slab_DiscountedCashFlowValuationTechniqueMember
Expected holding period 10 years
Estimated discount rate (as a percent) 2.96%slab_FairValueInputsLiquidityDiscount
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_AuctionRateSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= slab_DiscountedCashFlowValuationTechniqueMember