Common stock and convertible preferred stock - Warrants (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) shares	Oct. 06, 2020 $ / shares	Jun. 02, 2020 $ / shares
Volatility rate
Class of Warrant or Right [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.820	0.790
Risk-free interest rate
Class of Warrant or Right [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.002	0.002
Expected term (in years)
Class of Warrant or Right [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.027	0.030
Strike price (per share)
Class of Warrant or Right [Line Items]
Warrants and Rights Outstanding, Measurement Input		0.0900	0.0900
Warrants
Class of Warrant or Right [Line Items]
Warrant liability | shares	1,035,196
Fair Value of Warrants	$ 1.5
Warrant Liability	$ 7.1
Series A Preferred Stock
Class of Warrant or Right [Line Items]
Fair value of preferred stock | $ / shares		$ 12.00	$ 4.44