Post-retirement benefits - Components of Net Periodic Benefit (Income) Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Oct. 01, 2022	Sep. 30, 2023	Oct. 01, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans
—Employer service cost	$ 1.0	$ 0.8	$ 2.9	$ 2.5
—Interest cost	6.7	4.0	19.9	12.4
—Expected return on plan assets	(6.5)	(5.4)	(19.5)	(16.5)
—Net amortization of prior period (gains) losses	(0.9)	(0.2)	(2.6)	(0.7)
Net periodic benefit cost (income)	0.3	(0.8)	0.7	(2.3)
Cash Contributions	2.2	6.1	7.8	9.3
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans
—Employer service cost	1.0	0.8	2.9	2.5
—Interest cost	6.3	3.7	18.8	11.5
—Expected return on plan assets	(6.5)	(5.4)	(19.5)	(16.5)
—Net amortization of prior period (gains) losses	0.0	0.3	(0.1)	0.9
Net periodic benefit cost (income)	0.8	(0.6)	2.1	(1.6)
Cash Contributions	1.6	4.5	5.3	6.5
Other post-retirement benefits
Defined Benefit Plans and Other Postretirement Benefit Plans
—Employer service cost	0.0	0.0	0.0	0.0
—Interest cost	0.4	0.3	1.1	0.9
—Expected return on plan assets	0.0	0.0	0.0	0.0
—Net amortization of prior period (gains) losses	(0.9)	(0.5)	(2.5)	(1.6)
Net periodic benefit cost (income)	(0.5)	(0.2)	(1.4)	(0.7)
Cash Contributions	$ 0.6	$ 1.6	$ 2.5	$ 2.8