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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