Defined benefit pension plans - Components of Net Periodic Defined Benefit Pension Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined benefit pension plans [Line Items]
Service cost	$ 1.7	$ 1.6
Interest cost	5.4	5.6
Expected return on plan assets	(5.6)	(5.2)
Recognized net actuarial losses	0.9	0.9
Total	2.4	$ 2.9
Pension Plans Defined Benefit [Member]
Defined benefit pension plans [Line Items]
Expected contribution	$ 18.0