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Summary of Significant Accounting Policies - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | ---
Warrant Liability [Member] |  |
Liabilities: |  |
Liabilities, fair value | $ 13,197 |
Money Market Funds [Member] |  |
Assets: |  |
Assets, fair value | 30,318 | $ 25,764
Quoted Prices in Active Markets (Level 1) [Member] | Money Market Funds [Member] |  |
Assets: |  |
Assets, fair value | 30,318 | $ 25,764
Significant Unobservable Inputs (Level 3) [Member] | Warrant Liability [Member] |  |
Liabilities: |  |
Liabilities, fair value | $ 13,197 |

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