Property leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Impairment of right-of-use asset	$ 0	$ 289
Operating lease liability	$ 934
Discount rate (in percent)	8.00%
Weighted average remaining lease term	1 year 9 months 18 days
Operating lease expense	$ 651
Building
Lessee, Lease, Description [Line Items]
Right-of-use assets recognized with associated liability	$ 700
London | Building
Lessee, Lease, Description [Line Items]
Right-of-use assets recognized with associated liability		$ 600