Other non-current liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other non-current liabilities
Operating lease liability	$ 112,818	$ 111,322
Tax payable	19,706	20,232
Finance lease liability	17,109	16,336
Other	3,367	3,348
Total other non-current liabilities	$ 153,000	$ 151,238
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Total other non-current liabilities	Total other non-current liabilities