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Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Tax Credit Carryforward [Line Items] |  |  |  |
Change in valuation allowance | $ 1,792 | $ 2,253 | $ 515 |
Income tax holiday description | Profits generated from certain products of SMI Taiwan are exempted from income tax for five years beginning January 1, 2012. |  |  |
Tax holidays, tax savings amount | $ 4,648 | $ 906 | $ 2,573 |
Tax holidays, per share effect on earnings | $ 0.03 | $ 0.01 | $ 0.02 |
Accumulated undistributed earnings from a foreign subsidiary | $ 297,000 |  |  |
Deferred tax liability on undistributed foreign earnings | 0 |  |  |
Unrecognized tax benefit | 10,286 | $ 5,639 | $ 4,655 | $ 5,815
Total amount of interest expense and penalties | 575 | 363 | $ 343 |
Total amount of accrued interest and penalties | 2,587 | $ 1,977 |  |
Federal |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Net operating loss carryforwards for income tax purposes | $ 12,334 |  |  |
Federal net operating loss carryforwards expiration year | 2036 |  |  |
Research And Development | Federal |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Deferred tax assets tax credit carryforwards | $ 2,486 |  |  |
Tax credit carryforward expiration year for federal | 2036 |  |  |
Research And Development | State |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Deferred tax assets tax credit carryforwards | $ 1,742 |  |  |
Tax credit carryforward expiration year for state | No expiration date |  |  |
Taiwan |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Income tax exemption term | 5 years |  |  |
FCI | Research And Development |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Deferred tax assets tax credit carryforwards | $ 4,418 |  |  |
FCI | Research And Development | Minimum |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax credit carryforward expiration year for federal | 2017 |  |  |
FCI | Research And Development | Maximum |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax credit carryforward expiration year for federal | 2021 |  |  |

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