Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Future Issuance (Detail)

v3.21.1
Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Future Issuance (Detail) - shares
Dec. 31, 2020
Dec. 31, 2019
Class of Stock [Line Items]    
Common shares reserved for future issuance 28,028,978 8,143,816
Stock options    
Class of Stock [Line Items]    
Common shares reserved for future issuance 830,343 526,070
Restricted Stock Units    
Class of Stock [Line Items]    
Common shares reserved for future issuance 29,087 96,637
December 2020 Public Offering    
Class of Stock [Line Items]    
Common shares reserved for future issuance 5,260,000 0
Warrant liability | June 2016 Public Offering    
Class of Stock [Line Items]    
Common shares reserved for future issuance 421,867 421,867
Warrant liability | December 2020 Public Offering Series 1    
Class of Stock [Line Items]    
Common shares reserved for future issuance 6,800,000 0
Warrant liability | December 2019 Public Offering    
Class of Stock [Line Items]    
Common shares reserved for future issuance 4,472,205 4,472,205
Warrant liability | Warrants to purchase common stock associated with Solar loan agreement    
Class of Stock [Line Items]    
Common shares reserved for future issuance 12,243 12,243
Warrant liability | December 2020 Public Offering Series 2    
Class of Stock [Line Items]    
Common shares reserved for future issuance 6,800,000 0
Series 2 Warrant | March 2018 Public Offering    
Class of Stock [Line Items]    
Common shares reserved for future issuance 798,810 798,810
Option to Purchase Common Stock | December 2019 Public Offering    
Class of Stock [Line Items]    
Common shares reserved for future issuance 0 583,333
March 2019 Notes    
Class of Stock [Line Items]    
Common shares reserved for future issuance 1,138,200 1,138,200
April 2020 Notes    
Class of Stock [Line Items]    
Common shares reserved for future issuance 1,299,790 0
2014 Equity Incentive Plan    
Class of Stock [Line Items]    
Common shares reserved for future issuance 146,488 55,478
2014 Employee Stock Purchase Plan    
Class of Stock [Line Items]    
Common shares reserved for future issuance 5,895 7,423
2015 Inducement Award Plan    
Class of Stock [Line Items]    
Common shares reserved for future issuance 14,050 31,550