Employee benefits - Breakdown of pension and OPEB plans assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	$ 0	$ 17,792
Current liabilities	222	227
Non-current liabilities	8,068	8,552
OPEB Plan
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	0	0
Current liabilities	5,779	5,959
Non-current liabilities	$ 112,557	$ 153,999