Summary of significant accounting policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Warrants, notice period for nominal cash consideration	61 days
Prefunded Warrants
Lessee, Lease, Description [Line Items]
Outstanding pre-funded warrants (in shares)	12,663,010
Money market funds
Lessee, Lease, Description [Line Items]
Money market funds	$ 156.3	$ 108.3
Maximum | Office space
Lessee, Lease, Description [Line Items]
Lease term	12 months