Description of Business - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
Jan. 22, 2018	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Date of incorporation		Mar. 13, 2014
Class A common stock, par value \| $ / shares		$ 0.001
Reverse stock split	1-for-5
Reverse stock split, conversion ratio	5
Cash		$ 25,583	$ 5,562	$ 2,669
Net loss		28,623	28,024
Accumulated deficit		$ 94,992	$ 66,369

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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