Post-retirement benefits - Components of Net Periodic Benefit (Income) Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 29, 2024	Jul. 01, 2023	Jun. 29, 2024	Jul. 01, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans
—Employer service cost	$ 1.0	$ 0.9	$ 2.0	$ 1.9
—Interest cost	6.4	6.6	12.8	13.2
—Expected return on plan assets	(6.4)	(6.6)	(12.9)	(13.0)
—Net amortization of prior period losses (gains)	(0.6)	(0.8)	(1.2)	(1.7)
Net periodic benefit cost	0.4	0.1	0.7	0.4
Cash Contributions	2.3	2.4	4.9	5.6
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans
—Employer service cost	1.0	0.9	2.0	1.9
—Interest cost	6.1	6.3	12.2	12.5
—Expected return on plan assets	(6.4)	(6.6)	(12.9)	(13.0)
—Net amortization of prior period losses (gains)	0.2	(0.1)	0.4	(0.1)
Net periodic benefit cost	0.9	0.5	1.7	1.3
Cash Contributions	1.6	1.6	3.2	3.7
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	0.3	0.3	0.6	0.7
—Expected return on plan assets	0.0	0.0	0.0	0.0
—Net amortization of prior period losses (gains)	(0.8)	(0.7)	(1.6)	(1.6)
Net periodic benefit cost	(0.5)	(0.4)	(1.0)	(0.9)
Cash Contributions	$ 0.7	$ 0.8	$ 1.7	$ 1.9