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Stockholders' equity - Narrative (Details) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2022
Jun. 30, 2022
Mar. 31, 2022
Jun. 30, 2021
Sep. 30, 2022
Sep. 30, 2021
Dec. 31, 2013
Jun. 09, 2022
Jun. 08, 2022
Feb. 28, 2022
Dec. 31, 2021
May 31, 2020
Class of Stock [Line Items]                        
Preferred stock, shares authorized (in shares) 25,000,000       25,000,000           25,000,000  
Preferred stock, shares issued (in shares) 0       0           0  
Net proceeds from public offering of common stock         $ 110,954,000 $ 33,287,000            
Number of shares into which warrant issued during period may be converted (in shares)             129,491          
Warrant exercise price per share (in dollars per share)             $ 0.05          
Contractual life of warrants             10 years          
Number of shares of common stock into which warrants may be converted (in shares) 22,590       22,590              
Common stock, par value (in dollars per share) $ 0.0001       $ 0.0001     $ 0.0001     $ 0.0001  
Common stock, shares authorized (in shares) 350,000,000       350,000,000     350,000,000 175,000,000   175,000,000  
Common stock voting rights         The holders of the common stock are entitled to one vote for each share held.              
Common Stock                        
Class of Stock [Line Items]                        
Issuance of common stock under public offering, net of issuance costs (in shares) 1,382,631 9,904,964 13,169,903 2,271,074                
Exercise of common stock warrant in exchange for common stock (in shares)   16,654     16,654              
2020 ATM                        
Class of Stock [Line Items]                        
Amount of shares authorized to be offered and sold                       $ 100,000,000
2020 ATM | Common Stock                        
Class of Stock [Line Items]                        
Issuance of common stock under public offering, net of issuance costs (in shares)     11,740,210                  
Net proceeds from public offering of common stock     $ 54,800,000                  
2022 ATM                        
Class of Stock [Line Items]                        
Amount of shares authorized to be offered and sold                   $ 100,000,000    
2022 ATM | Common Stock                        
Class of Stock [Line Items]                        
Issuance of common stock under public offering, net of issuance costs (in shares)         12,717,288              
Net proceeds from public offering of common stock         $ 56,500,000              
Remaining unsold and available amount $ 42,400,000       $ 42,400,000