Common stock and convertible preferred stock - Warrants (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Jun. 30, 2020
Warrants
Class of Warrant or Right [Line Items]
Warrant liability	1,023,530
Fair Value of Warrants	$ 1.5
Warrant Liability	$ 7.1
Warrants exercised, numbers	11,666
Exercise price	$ 9.00
Gross proceeds from issuance of warrants	$ 0.1
Exercise of common stock warrants (shares)	11,666
Series A Preferred Convertible Stock
Class of Warrant or Right [Line Items]
Fair Value of Warrants		$ 1.5
Exercise price		$ 9.00