Defined benefit pension plans - Components of Net Periodic Defined Benefit Pension Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined benefit pension plans [Line Items]
Service cost	$ 1.4	$ 1.7
Interest cost	5.2	5.4
Expected return on plan assets	(5.1)	(5.6)
Recognized net actuarial losses	0.6	0.9
Total	2.1	$ 2.4
Pension plans defined benefit
Defined benefit pension plans [Line Items]
Expected contribution	$ 16.0