Income taxes - Provision for 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 Disclosure [Abstract]
Income tax (provision) benefit	$ (456)	$ 1,206	$ (1,279)	$ (1,199)