Pensions and other postretirement benefit plans - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Employee retirement contributions deferred	$ 11.0
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Contribution to the defined benefit plans	10.2
Pension Plans | Foreign
Defined Benefit Plan Disclosure [Line Items]
Deferred contributions by employer in response to COVID-19	12.0
Pension Plans | U.S. | Subsequent Event | Forecasted
Defined Benefit Plan Disclosure [Line Items]
Deferred contributions by employer in response to COVID-19		$ 5.0
OPEB
Defined Benefit Plan Disclosure [Line Items]
Contribution to the defined benefit plans	$ 4.3