Quarterly report pursuant to Section 13 or 15(d)

Debt - Additional Information (Details)

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Debt - Additional Information (Details)
3 Months Ended 9 Months Ended
Sep. 08, 2015
USD ($)
$ / shares
shares
Sep. 30, 2015
USD ($)
$ / shares
shares
Sep. 30, 2014
USD ($)
Sep. 30, 2015
USD ($)
installment
$ / shares
shares
Sep. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
Dec. 31, 2014
USD ($)
Aug. 11, 2014
USD ($)
Jun. 30, 2014
USD ($)
Dec. 31, 2013
USD ($)
Debt Instrument [Line Items]                    
Original principal amount   $ 20,990,000   $ 20,990,000     $ 24,500,000      
Cash and cash equivalents   11,268,000 $ 10,360,000 11,268,000 $ 10,360,000   18,247,000     $ 2,279,000
Proceeds from issuance of common stock, net of issuance costs $ 5,000,000                  
Loss on extinguishment of debt   (2,403,000) $ 0 (2,324,000) 1,596,000          
Repayments of long-term debt       1,158,000 $ 18,000,000          
Hercules Term Loan                    
Debt Instrument [Line Items]                    
Original principal amount   18,841,000   $ 18,841,000     20,000,000   $ 20,000,000  
Debt and line of credit maturity date       Jan. 01, 2018            
Term loan fee amount                 200,000  
Final payment fee for debt   $ 1,700,000   $ 1,700,000         1,500,000  
Debt description       The Hercules Term Loan also includes a non-refundable final payment fee of $1.7 million.  The final payment fee is being accrued and recorded to interest expense over the life of the loan.            
Debt instrument, fixed rate   10.95%   10.95%            
Debt instrument, interest rate description       The Hercules Term Loan bears interest at the rate of the greater of either (i) the prime rate plus 7.7%, and (ii) 10.95%.             
Debt instrument, periodic payment, principal       $ 700,000            
Term loan, payment terms        Interest accrues from the closing date of the loan and interest payments are due monthly. Principal payments are required commencing August 1, 2015 and are to be made in 30 equal installments of approximately $700,000, with the remainder due at maturity.             
Debt instrument, covenant description       Additionally, the Amendment reduced the Company’s obligation to maintain cash and cash equivalents of not less than $9.0 million to an amount that varies based on the loan amount. The minimum cash requirement is reduced by $500,000 for every $1.0 million paid in principal to a minimum of $2.5 million. The minimum cash and cash equivalents balance required to maintain compliance with the minimum liquidity covenant at September 30, 2015 was $8.5 million.            
Debt instrument, covenant compliance       Although the Company was in compliance with the liquidity covenant at September 30, 2015, the Company anticipates that it will be non-compliant with the liquidity covenant during the fourth quarter of 2015 if additional financing is not obtained, and has therefore classified the entire obligation as a current liability.            
Hercules Term Loan | Maximum                    
Debt Instrument [Line Items]                    
Number of installments for principal payments | installment       30            
Hercules Term Loan | Prime rate plus                    
Debt Instrument [Line Items]                    
Debt instrument, variable interest rate       7.70%            
Hercules Term Loan, The Amendment                    
Debt Instrument [Line Items]                    
Final payment fee for debt   $ 1,700,000   $ 1,700,000            
Interest rate increase (decrease)       1.50%            
Percentage of prepayment amount       1.50%            
Percentage of prepayment amount thereafter       0.75%            
Hercules Term Loan, Liquidity Covenant                    
Debt Instrument [Line Items]                    
Cash and cash equivalents   8,500,000   $ 8,500,000   $ 9,000,000        
Debt instrument, periodic payment, principal       1,000,000            
Cash requirement reduction   500,000   500,000            
Cash requirement minimum   2,500,000.0   2,500,000.0            
Conversion Feature of Note                    
Debt Instrument [Line Items]                    
Original principal amount                 2,900,000  
Debt instrument purchase price                 $ 2,500,000  
Repayments of debt 800,000                  
Magna August Note                    
Debt Instrument [Line Items]                    
Original principal amount   $ 2,149,000   $ 2,149,000       $ 3,500,000    
Debt instrument purchase price               $ 3,500,000    
Repayments of debt 1,400,000                  
Amount agreed to be paid to redeem additional convertible debt if certain equity proceeds threshold is met 1,250,000                  
Repayments of additional convertible debt 1,100,000                  
Magna Convertible Notes                    
Debt Instrument [Line Items]                    
Original principal amount             $ 4,500,000      
Loss on extinguishment of debt (2,400,000)                  
Convertible debt fair value 3,500,000                  
Convertible Debt [Member] | Magna August Note                    
Debt Instrument [Line Items]                    
Debt instrument, fixed rate   6.00%   6.00%            
Convertible Debt [Member] | Magna Exchange Convertible Notes                    
Debt Instrument [Line Items]                    
Debt conversion original debt amount       $ 202,000            
Number of shares converted | shares       373,000            
Loss on extinguishment of debt       $ 79,000            
Convertible Debt [Member] | Magna Exchange Convertible Notes, Mature on August 11, 2016                    
Debt Instrument [Line Items]                    
Debt and line of credit maturity date       Aug. 11, 2016            
September 2015 Offering                    
Debt Instrument [Line Items]                    
Proceeds from warrant exercises       $ 5,000,000            
Outstanding warrants exercisable | shares   13,123,360   13,123,360            
Exercise price of warrants (in usd per share) | $ / shares   $ 0.47   $ 0.47            
Proceeds from offering $ 2,500,000                  
Proceeds from issuance of common stock, net of issuance costs       $ 131,000            
September 2015 Offering                    
Debt Instrument [Line Items]                    
Proceeds from warrant exercises       $ 10,000,000            
Hercules Warrant [Member]                    
Debt Instrument [Line Items]                    
Outstanding warrants exercisable | shares 1,548,387                  
Exercise price of warrants (in usd per share) | $ / shares $ 0.47                  
Warrants and Rights Outstanding $ 382,000                  
Magna Warrant [Member]                    
Debt Instrument [Line Items]                    
Common stock, authorized, shares | shares   568,889   568,889            
Exercise price of warrants (in usd per share) | $ / shares   $ 4.65   $ 4.65