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Fair Value Measurements - Additional Information (Detail) | 3 Months Ended
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Mar. 31, 2018 USD ($) shares
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |
Warrant liability | $ 0
Change in fair value of level 3 financial liabilities | $ 0
Maximum maturity period of cash and cash equivalents | 90 days
Maximum maturity period of short-term investments | 1 year
Series A and Series B Warrants issued in July 2014 Financing [Member] |
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |
Warrants outstanding and exercisable | shares | 0
Maximum [Member] |
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] |
Maturity period of securities | 1 year

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