Defined contribution and defined benefit retirement plans - Components of Net Periodic Benefit Cost (Detail) - Defined benefit pension plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Foreign Pension Plans Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6.3	$ 11.3	$ 14.7
Interest cost	19.7	10.5	8.2
Expected return on plan assets	(18.2)	(11.0)	(11.2)
Amortization of prior service cost	0.1	0.1	0.2
Recognized actuarial losses	1.8	12.5	19.4
Settlements	1.6	0.3
Total	11.3	23.7	31.3
U S
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.7	0.4	0.5
Expected return on plan assets	(0.6)	(0.6)	(0.6)
Recognized actuarial losses	0.6	0.6	0.6
Settlements			$ 0.5
Total	$ 0.7	$ 0.4