Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Shares (Details) - shares
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Stock options    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities (in shares) 5,310,498 4,152,734
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) 14,033 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 13,313,625
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) 13,008,000 0