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Summary Of Significant Accounting Policies - Additional Information (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 USD ($) Customer	Dec. 31, 2013 USD ($) Customer	Dec. 31, 2012 USD ($) Customer	Dec. 31, 2012 TWD	Dec. 31, 2014 Customers accounted for 10% or more Net revenue	Dec. 31, 2013 Customers accounted for 10% or more Net revenue	Dec. 31, 2012 Customers accounted for 10% or more Net revenue	Dec. 31, 2014 Amended in August 2012 TWD	Dec. 31, 2014 Minimum	Dec. 31, 2014 Maximum	Dec. 31, 2014 American Depositary Shares	Dec. 31, 2013 American Depositary Shares	Dec. 31, 2012 American Depositary Shares	Dec. 31, 2014 Ordinary Shares	Dec. 31, 2013 Ordinary Shares	Dec. 31, 2012 Ordinary Shares	Dec. 31, 2014 Software Minimum	Dec. 31, 2014 Software Maximum	Dec. 31, 2014 Core technology and customer relationship	Dec. 31, 2014 Buildings Minimum	Dec. 31, 2014 Buildings Maximum	Dec. 31, 2014 Machinery and Equipment Minimum	Dec. 31, 2014 Machinery and Equipment Maximum	Dec. 31, 2014 Furniture and Fixtures Minimum	Dec. 31, 2014 Furniture and Fixtures Maximum	Dec. 31, 2014 Leasehold And Building Improvement Minimum	Dec. 31, 2014 Leasehold And Building Improvement Maximum	Dec. 31, 2014 FCI
Significant Accounting Policies [Line Items]
Consolidated interest acquire in subsidiary	100.00%simo_PercentageOfOwnershipInterestAcquired																											99.90%simo_PercentageOfOwnershipInterestAcquired / dei_LegalEntityAxis = simo_FciIncMember
Top ten customer sales in percentage	76.00%simo_PercentageOfTotalRevenueAccountedForByTopTenCustomers	76.00%simo_PercentageOfTotalRevenueAccountedForByTopTenCustomers	75.00%simo_PercentageOfTotalRevenueAccountedForByTopTenCustomers	75.00%simo_PercentageOfTotalRevenueAccountedForByTopTenCustomers
Major customers percentage of net sales					47.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_SalesRevenueNetMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CustomerConcentrationRiskMember	46.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_SalesRevenueNetMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CustomerConcentrationRiskMember	35.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_SalesRevenueNetMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CustomerConcentrationRiskMember
Number of customers accounted for 10% or more sales	2simo_NumberOfCustomersAccountingForTenPercentOrMoreOfConsolidatedRevenue	2simo_NumberOfCustomersAccountingForTenPercentOrMoreOfConsolidatedRevenue	1simo_NumberOfCustomersAccountingForTenPercentOrMoreOfConsolidatedRevenue	1simo_NumberOfCustomersAccountingForTenPercentOrMoreOfConsolidatedRevenue
Short term investment maturity period									3 months	1 year
Property plant and equipment estimated useful life																	1 year	5 years		25 years	50 years	3 years	6 years	3 years	8 years	2 years	6 years
Depreciation and amortization	$ 6,917us-gaap_DepreciationDepletionAndAmortization	$ 6,429us-gaap_DepreciationDepletionAndAmortization	$ 5,881us-gaap_DepreciationDepletionAndAmortization
Intangible asset amortized over estimated useful lives																			4 years
Warranty period for manufacturing defects of products	1 year
Evaluation of tax benefits realized upon settlement	50.00%simo_PercentageOfIncomeTaxExaminationMinimumLikelihoodOfTaxBenefitsBeingRealizedUponUltimateSettlement
Income tax under IBT act effective date	January 1, 2006
Minimum Alternative Tax On Income under IBT act	12.00%simo_MinimumAlternativeTaxOnIncomeAtForeignCountry
Standard deduction tax amount				1,000us-gaap_IncomeTaxReconciliationDeductions				500us-gaap_IncomeTaxReconciliationDeductions / us-gaap_IncomeTaxAuthorityAxis = simo_AmendedMember
Standard deduction tax rate			10.00%us-gaap_EffectiveIncomeTaxRateReconciliationDeductionsOther	10.00%us-gaap_EffectiveIncomeTaxRateReconciliationDeductionsOther				12.00%us-gaap_EffectiveIncomeTaxRateReconciliationDeductionsOther / us-gaap_IncomeTaxAuthorityAxis = simo_AmendedMember
Amendment Effective Date								January 1, 2013
The effect of dilutive securities of employee stock options and restricted stock units											546us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis = simo_AmericanDepositaryShareMember	577us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis = simo_AmericanDepositaryShareMember	1,311us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis = simo_AmericanDepositaryShareMember	2,183us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember	2,308us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember	5,245us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember

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Minimum Alternative Tax On Income At Foreign Country

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Number Of Customers Accounting For Ten Percent Or More Of Consolidated Revenue

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Percentage Of Income Tax Examination Minimum Likelihood of Tax Benefits Being Realized Upon Ultimate Settlement

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Percentage of Ownership Interest Acquired

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Percentage of Total Revenue Accounted for by Top Ten Customers

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Short Term Investments, Maturity Period

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deductions. Including, but not limited to, extraterritorial income exclusion deduction, qualified production activity deduction, dividend deduction, deduction for dividend paid to employee stock ownership plan, Medicare prescription drug benefit subsidy deduction, and other deductions.

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