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Redeemable Convertible Preferred Stock and Common Stock - Additional Information (Detail)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
USD ($)
$ / shares
Sep. 30, 2016
USD ($)
Sep. 30, 2017
USD ($)
Installment
$ / shares
shares
Sep. 30, 2016
USD ($)
Aug. 01, 2017
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
May 31, 2012
shares
Temporary Equity [Line Items]              
Accretion amount | $ $ 10 $ 10 $ 40 $ 40      
Common Stock              
Temporary Equity [Line Items]              
Shares issued during period     260,163        
Common Stock | Restricted Stock Units (RSUs)              
Temporary Equity [Line Items]              
Shares issued in connection with Employee Stock Purchase Plan and vesting of restricted stock units     61,747        
Maximum | Repricing Agreement              
Temporary Equity [Line Items]              
Limitations for issuance of common stock or voting power outstanding to holder, in percentage         19.99%    
Series A Convertible Preferred Stock              
Temporary Equity [Line Items]              
Warrants to purchase common stock             325,000
Cumulative dividends at a rate     6.00%        
Redeemable convertible preferred stock, liquidation preference per share | $ / shares $ 5.00   $ 5.00        
Common stock issued as payment of accrued preferred dividends     198,416        
Series A Convertible Preferred Stock | Common Stock | Repricing Agreement              
Temporary Equity [Line Items]              
Conversion price per share | $ / shares         $ 2.26    
Convertible preferred stock, shares issuable upon conversion         2,212,389    
Series A Convertible Preferred Stock | Scenario, Plan              
Temporary Equity [Line Items]              
Redeemable convertible preferred stock, liquidation preference per share | $ / shares 5.00   $ 5.00        
Redemption price per share | $ / shares $ 5.00   $ 5.00     $ 5.00  
Number of redemption price, accrued and unpaid dividends installment payments | Installment     36        
Annual interest rate on redemption value payable     6.00%        
Series A Convertible Preferred Stock | Scenario, Plan | Maximum              
Temporary Equity [Line Items]              
Majority outstanding shares redeemable date     Apr. 30, 2017        
Series A Convertible Preferred Stock | Accounts Payable and Other Accrued Expenses              
Temporary Equity [Line Items]              
Total accrued but unpaid dividends | $ $ 80   $ 80     $ 230  
Series A Warrants | Common Stock | Repricing Agreement              
Temporary Equity [Line Items]              
Warrants to purchase common stock         125,000    
Warrant exercise price per share | $ / shares         $ 2.72    
Series B Warrants | Common Stock | Repricing Agreement              
Temporary Equity [Line Items]              
Warrants to purchase common stock         200,000    
Warrant exercise price per share | $ / shares         $ 3.17