Summary of significant accounting policies - Reconciliation of cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 579,350	$ 405,511
Restricted cash included in prepayments and other current assets	1,800	0
Total cash, cash equivalents and restricted cash reported in the consolidated statements of cash flows	$ 581,150	$ 405,511	$ 448,612	$ 752,618
Restricted Cash, Statement of Financial Position [Extensible Enumeration]	Prepayments and other current assets