Deferred Income Tax Assets (liabilities) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current:
Notes and accounts receivable	$ 141	$ 142
Stock-based compensation	615	679
Allowance for sales return	105	123
Inventory reserve	48	544
Foreign currency translation	(1,273)	312
Others	504us-gaap_DeferredTaxAssetsOther	561us-gaap_DeferredTaxAssetsOther
Valuation allowance	(528)	(1,083)
Deferred Tax Assets, Net of Valuation Allowance, Current	(388)us-gaap_DeferredTaxAssetsNetCurrent	1,278us-gaap_DeferredTaxAssetsNetCurrent
Non-current:
Inventory reserve	766	590
Property and equipment	452	651
Investment tax credits	7,823	7,011
Net operating loss carryforwards	9,621	8,540
Others	(490)simo_DeferredTaxAssetsOtherNonCurrent	(885)simo_DeferredTaxAssetsOtherNonCurrent
Valuation allowance	(16,263)	(15,193)
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	$ 1,909us-gaap_DeferredTaxAssetsNetNoncurrent	$ 714us-gaap_DeferredTaxAssetsNetNoncurrent

Deferred Tax Assets Accounts Receivable and Advance Payments

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Deferred Tax Assets, Inventory Reserves and Valuation

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards expected to be realized or consumed within one year or operating cycle, if longer.

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Amount after allocation of valuation allowances of noncurrent deferred tax asset attributable to deductible temporary differences and carryforwards. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from property, plant, and equipment.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from estimated returns and sales allowances.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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