Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Examination [Line Items]
Income tax expense (benefit)	$ 2,633	$ (99)	$ 4,655	$ (3,594)
Effective tax rate, percentage	126.30%	8.10%	829.80%	31.30%
United Kingdom
Income Tax Examination [Line Items]
Discrete tax expense			$ 500