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Stockholders' Equity - February 2018 Financing - Additional Information (Details)
$ / shares in Units, $ in Millions
 1 Months Ended
Sep. 30, 2018
shares
Feb. 28, 2018
USD ($)
$ / shares
shares
Dec. 31, 2018
$ / shares
shares
Dec. 31, 2017
$ / shares
shares
Dec. 31, 2016
$ / shares
shares
Stockholders Equity Note [Line Items]          
Sale of common stock, net of expenses (in shares) 4,667,811 424,000      
Number of pre-funded warrants   76,000      
Net proceeds from issuance of private placement | $   $ 4.3      
Warrants exercisable per share price (in dollars per share) | $ / shares     $ 0.22 $ 1,569 $ 910,000
Number of warrants outstanding (in shares)     65,685,269 14,049 78
February 2018 Warrants [Member]          
Stockholders Equity Note [Line Items]          
Warrants issued to purchase Common Stock   1,000,000      
Value of warrants issued | $   $ 18.3      
Warrants exercisable per share price (in dollars per share) | $ / shares     $ 10.00    
Number of warrants outstanding (in shares)     200,000    
February 2018 Warrants [Member] | Exercise Price [Member]          
Stockholders Equity Note [Line Items]          
Warrants measurement input | $ / shares   10.00      
February 2018 Warrants [Member] | Contractual Term [Member]          
Stockholders Equity Note [Line Items]          
Warrants expiration period   6 years      
February 2018 Warrants [Member] | Volatility [Member]          
Stockholders Equity Note [Line Items]          
Warrants measurement input   1.2268      
February 2018 Warrants [Member] | Risk Free Rate [Member]          
Stockholders Equity Note [Line Items]          
Warrants measurement input   0.01