Defined contribution and defined benefit retirement plans - Schedule of Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Details) - Pension Plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Plans Postretirement And Other Employee Benefits [Line Items]
Net actuarial gains (losses)	$ 39.0	$ 16.0	$ (25.5)
Amortization of unrecognized net actuarial losses	3.1	3.7	3.8
Amortization of unrecognized prior service cost (credit)	0.1	0.1
Settlement loss	29.0	0.4	6.5
Total	$ 71.2	$ 20.2	$ (15.2)