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Organization and Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands |  |  | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2016 USD ($) $ / shares shares | Aug. 16, 2016 $ / shares shares | Jul. 31, 2016 | Dec. 31, 2016 USD ($) shares | Dec. 31, 2015 USD ($) shares | Dec. 31, 2014 shares | Dec. 31, 2013 shares
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Reverse stock split description |  |  |  | In July 2016, the Company's board of directors approved an amendment to the Company's amended and restated certificate of incorporation to effect a reverse split of the Company's issued and outstanding common stock at a 1-for-14.5 ratio, which was effected on August 1, 2016. |  |  |
Reverse stock split effective date |  |  |  | Aug. 01, 2016 |  |  |
Reverse stock split ratio |  |  | 0.06896 |  |  |  |
Proceeds from stock issuance, net of underwriting discounts, commissions | $ |  |  |  | $ 83,648 |  |  |
Number of shares converted |  | 8,577,571 |  |  |  |  |
Preferred stock outstanding |  |  |  | 0 | 77,185,117 |  |
Accumulated deficit | $ |  |  |  | $ (64,593) | $ (27,416) |  |
Cash, cash equivalents and available-for-sale securities | $ |  |  |  | $ 87,700 |  |  |
Common Stock [Member] |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Common stock issued |  |  |  | 7,752,972 |  |  |
Initial Public Offering [Member] |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Proceeds from stock issuance, net of underwriting discounts, commissions | $ | $ 83,600 |  |  |  |  |  |
Common stock issued | 252,972 | 7,500,000 |  |  |  |  |
Common stock price per share | $ / shares | $ 12.00 | $ 12.00 |  |  |  |  |
Initial Public Offering [Member] | Common Stock [Member] |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Number of shares converted |  | 8,577,571 |  |  |  |  |
Redeemable Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Preferred stock outstanding |  |  |  |  | 77,185,117 | 42,037,500 | 24,037,500
Redeemable Convertible Preferred Stock [Member] | Initial Public Offering [Member] |  |  |  |  |  |  |
Organization Consolidation And Presentation Of Financial Statements [Line Items] |  |  |  |  |  |  |
Preferred stock outstanding |  | 0 |  |  |  |  |

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