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Short-Term Bank Loans - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2016 USD ($) Bank | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Short-term Debt [Line Items] |  |  |
Interest expense | $ 105,000 | $ 0 | $ 0
Number of banks | Bank | 2 |  |
Line of credit | $ 95,000,000 |  |
Securities Loan | 25,000,000 |  |
Pledged deposit | 25,000,000 |  |
Loans payable | $ 25,000,000 |  |
Minimum |  |  |
Short-term Debt [Line Items] |  |  |
Interest rate | 0.953% |  |
Maximum |  |  |
Short-term Debt [Line Items] |  |  |
Interest rate | 1.51% |  |

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