Annual report pursuant to Section 13 and 15(d)

Capital Stock - Common Stock Warrants - Additional Information (Details)

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Capital Stock - Common Stock Warrants - Additional Information (Details) - USD ($)
 1 Months Ended 12 Months Ended
Feb. 29, 2016
Feb. 28, 2015
Sep. 30, 2012
Mar. 31, 2012
Dec. 31, 2016
Dec. 31, 2014
Dec. 31, 2017
Class Of Warrant Or Right [Line Items]              
Aggregate number of unregistered shares of common stock called by warrants (in shares) 8,249            
Exercise price of warrants (in dollars per share) $ 15.40            
Exercisable period of warrants 5 years            
Warrants expiration period 2021-02            
Estimated fair value of warrants $ 100,000            
Warrants outstanding (in shares)         498,556   17,312
Five Year Warrants Issued in February 2015 [Member] | Hercules Loan [Member]              
Class Of Warrant Or Right [Line Items]              
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          
Exercisable period of warrants   5 years          
Two Year Warrants Issued in December 2014 [Member]              
Class Of Warrant Or Right [Line Items]              
Exercise price of warrants (in dollars per share)           $ 158.01  
Warrant term           2 years  
Warrants outstanding (in shares)           404,833  
Warrants expiration period           2016-12  
December 2014 Revalued Warrants [Member]              
Class Of Warrant Or Right [Line Items]              
Gain (loss) on revaluation of warrant liability         $ 3,000,000    
Five Year Warrants Issued in September 2012 [Member] | GECC Term Loan [Member]              
Class Of Warrant Or Right [Line Items]              
Aggregate number of unregistered shares of common stock called by warrants (in shares)     1,967        
Exercise price of warrants (in dollars per share)     $ 70.80        
Exercisable period of warrants     5 years        
Warrants expiration period     2017-09        
Five Year Warrants Issued in March 2012 [Member]              
Class Of Warrant Or Right [Line Items]              
Aggregate number of unregistered shares of common stock called by warrants (in shares)       741,729      
Exercise price of warrants (in dollars per share)       $ 35.20      
Estimated fair value of warrants         0    
Warrant term       5 years      
Warrants expiration period       2017-03      
March 2012 Revalued Warrants [Member]              
Class Of Warrant Or Right [Line Items]              
Gain (loss) on revaluation of warrant liability         $ 7,500,000