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Income Taxes - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Tax Credit Carryforward [Line Items]      
Change in valuation allowance $ 515us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount $ 1,075us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount $ (3,271)us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Income tax exemption term 5 years    
Income tax holiday description Profits generated from certain products of SMI Taiwan are exempted from income tax for five years beginning January 1, 2010 and January 1, 2012    
Unrecognized tax benefits that would affect effective tax rate 4,655us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate    
Total amount of interest expense and penalties 343us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense 627us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense 499us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense
Total amount of accrued interest and penalties 1,674us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued 1,412us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued  
Federal      
Tax Credit Carryforward [Line Items]      
Net operating loss carryforwards for income tax purposes 7,794us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= simo_FederalMember		    
Federal net operating loss carryforwards expiration year 2024    
Research And Development | Federal      
Tax Credit Carryforward [Line Items]      
Deferred tax assets tax credit carryforwards 2,391us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
/ us-gaap_IncomeTaxAuthorityAxis
= simo_FederalMember
/ us-gaap_TaxCreditCarryforwardAxis
= simo_ResearchAndDevelopmentMember		    
Tax credit carryforward expiration year for federal 2023    
Research And Development | State      
Tax Credit Carryforward [Line Items]      
Deferred tax assets tax credit carryforwards 1,678us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
/ us-gaap_IncomeTaxAuthorityAxis
= simo_StateMember
/ us-gaap_TaxCreditCarryforwardAxis
= simo_ResearchAndDevelopmentMember		    
Tax credit carryforward expiration year for state No expiration date    
FCI | Research And Development      
Tax Credit Carryforward [Line Items]      
Deferred tax assets tax credit carryforwards $ 3,754us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch
/ dei_LegalEntityAxis
= simo_FciIncMember
/ us-gaap_TaxCreditCarryforwardAxis
= simo_ResearchAndDevelopmentMember		    
FCI | Research And Development | Minimum      
Tax Credit Carryforward [Line Items]      
Tax credit expiration period 2015    
FCI | Research And Development | Maximum      
Tax Credit Carryforward [Line Items]      
Tax credit expiration period 2019