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Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Jan. 22, 2018 | Apr. 30, 2018 USD ($) $ / shares shares | Mar. 31, 2018 USD ($) Subsidiary | Dec. 31, 2017 USD ($) | Mar. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Description Of Business [Line Items] |  |  |  |  |  |
Date of incorporation |  |  | Mar. 13, 2014 |  |  |
Number of wholly-owned subsidiaries | Subsidiary |  |  | 2 |  |  |
Reverse stock split | 1-for-5 |  |  |  |  |
Reverse stock split, conversion ratio | 5 |  |  |  |  |
Cash |  |  | $ 4,395 | $ 5,562 | $ 7,666 | $ 2,669
Subsequent Event | Underwritten Public Offering |  |  |  |  |  |
Description Of Business [Line Items] |  |  |  |  |  |
Warrants to purchase number of common stock, shares | shares |  | 2,463,185 |  |  |  |
Price per share | $ / shares |  | $ 7.47 |  |  |  |
Net proceeds from offering after deducting underwriting discounts and commissions |  | $ 17,300 |  |  |  |
Estimated offering expenses |  | $ 1,000 |  |  |  |
Subsequent Event | Common Stock | Underwritten Public Offering |  |  |  |  |  |
Description Of Business [Line Items] |  |  |  |  |  |
Shares issued | shares |  | 2,463,185 |  |  |  |

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