Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Shares (Details)

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Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Shares (Details) - shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 80,495,169 29,706,272
Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 44,722,222 0
Outstanding stock options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 5,261,860 4,052,913
Outstanding restricted stock units    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 966,394 111,891
Option to purchase common stock    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 5,833,333 0
Warrants to purchase Series C-1 Preferred | Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 14,033
Warrants to purchase common stock associated with Solar loan agreement | Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 122,435 122,435
Warrants to purchase common stock associated with June 2016 Public Offering | Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 4,218,750 4,218,750
March 2018 Public Offering Series 1 [Member] | Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 0 13,198,075
March 2018 Public Offering Series 2 [Member] | Warrant liability    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 7,988,175 7,988,175
Common stock associated with 6% convertible senior notes    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 11,382,000 0