Employee plans - Components of Net Periodic Benefit Expense (Details) - USD ($) $ in Millions		1 Months Ended		12 Months Ended
	Oct. 14, 2021	Jan. 31, 2021	Dec. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 130.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]				Other (expense), net
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Settlement loss					$ 499.4
Pension Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost				$ 0.0	0.0	$ 0.0
Interest cost				114.6	117.6	162.5
Expected return on plan assets				(189.8)	(199.8)	(208.6)
Amortization of prior service credit				(2.5)	(2.5)	(2.5)
Recognized net actuarial loss				125.9	135.6	135.5
Settlement loss		$ 158.0	$ 142.1	0.0	288.1	142.1
Net periodic pension expense (income)				48.2	339.0	229.0
Pension Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost				1.9	3.0	2.8
Interest cost				39.3	36.7	53.4
Expected return on plan assets				(77.4)	(81.6)	(90.6)
Amortization of prior service credit				(2.6)	(2.8)	(2.5)
Recognized net actuarial loss				37.7	48.3	43.2
Settlement loss				0.0	211.3	0.0
Net periodic pension expense (income)				(1.1)	214.9	6.3
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost				0.2	0.4	0.5
Interest cost				1.9	1.8	4.4
Expected return on plan assets				(0.3)	(0.3)	(0.4)
Amortization of prior service credit				(1.4)	(1.7)	(1.6)
Recognized net actuarial loss				(2.2)	(2.1)	1.0
Net periodic pension expense (income)				$ (1.8)	$ (1.9)	$ 3.9