Common stock - Warrants (Details) - Warrants - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Class of Warrant or Right [Line Items]
Warrants exercised, numbers	0	100,695
Gross proceeds from issuance of warrants		$ 0.9
Exercise of common stock warrants (shares)		100,695
Additional warrants exercised on cashless		72,320
Shares issued in cashless exercise		45,322
Exercise Price $9.00
Class of Warrant or Right [Line Items]
Warrants outstanding	803,112
Exercise price	$ 9.00
Exercise Price $45.00
Class of Warrant or Right [Line Items]
Warrants outstanding	500,000
Exercise price	$ 45.00