Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - Hercules Term Loan - Additional Information (Details)

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Long-Term Debt - Hercules Term Loan - Additional Information (Details) - USD ($)
3 Months Ended 6 Months Ended
Feb. 27, 2015
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Debt Instrument [Line Items]            
Carrying value of the loan   $ 27,861,000   $ 27,861,000    
Loss on extinguishment of debt       $ (515,000)    
Hercules Term Loan [Member]            
Debt Instrument [Line Items]            
Maturity date Sep. 01, 2018          
Variable rate basis       The Hercules Term Loan had a variable interest rate that was the greater of either (i) 9.40% plus the prime rate as reported from time to time in The Wall Street Journal minus 7.25%, or (ii) 9.40%.    
Period of principal and interest amortized 30 months          
Amortization of interest payments period end date Jun. 01, 2016          
Period of interest 1 month          
Additional interest rate in case of default 5.00%          
Debt issuance costs $ 500,000          
Final payment fee $ 1,200,000          
Amortization of debt discount   $ 0 $ 200,000 $ 200,000 $ 300,000  
Outstanding principal balance           $ 17,500,000
Carrying value of the loan           $ 16,900,000
Prepayment charge not required to pay       1.00%    
Loss on extinguishment of debt       $ 500,000    
Aggregate number of unregistered shares of common stock called by warrants (in shares) 9,063          
Exercise price of warrants (in dollars per share) $ 66.20          
Estimated fair value of warrants $ 500,000          
Exercisable period of warrants 5 years          
Warrants expiration period 2020-02          
Minimum [Member] | Hercules Term Loan [Member]            
Debt Instrument [Line Items]            
Percentage bearing variable rate   9.40%   9.40%    
Prime Rate [Member] | Hercules Term Loan [Member]            
Debt Instrument [Line Items]            
Basis spread, addition       9.40%    
Basis spread, subtraction   7.25%   7.25%