Annual report pursuant to Section 13 and 15(d)

Income taxes - Additional information (Details)

v3.21.1
Income taxes - Additional information (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Tax Disclosure [Abstract]      
Effective tax rate 0.00% 0.00%  
Current income tax expense   $ 0  
Deferred income tax expense $ 0 0  
Valuation allowance $ 16,724,000 $ 7,913,000 $ 0