Employee Retirement Plans and Postretirement Benefits - Net Periodic Pension (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) pension_plan	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 26, 2024 pension_plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 150.5	$ 162.9
Total other pension and postretirement (benefit) cost, net	$ 5.0	(10.2)	$ (36.6)
Purchased annuity contracts, number of Canadian pension plans | pension_plan	2			2
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.1	0.9	1.3
Interest cost	129.7	140.4	103.9
Expected return on plan assets, net of expenses	(169.8)	(157.8)	(154.2)
Amortization of prior service (benefit) cost	0.3	0.3	0.3
Amortization of net actuarial (gain) loss	18.1	17.1	5.6
Curtailment, settlement or special termination benefit (gain) loss	34.0	0.0	2.9
Expected participant contributions	0.0	(0.3)	(0.3)
Total other pension and postretirement (benefit) cost, net	12.3	(0.3)	(41.8)
Net periodic pension and OPEB (benefit) cost	12.4	0.6	(40.5)
Pension | Canadian Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Curtailment, settlement or special termination benefit (gain) loss	34.0		8.0
Pension | U.S. Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Curtailment, settlement or special termination benefit (gain) loss			5.3
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	3.6	3.3	5.5
Interest cost	20.8	22.5	16.1
Expected return on plan assets, net of expenses	0.0	0.0	0.0
Amortization of prior service (benefit) cost	(0.7)	(0.7)	(0.7)
Amortization of net actuarial (gain) loss	(27.4)	(31.7)	(10.2)
Curtailment, settlement or special termination benefit (gain) loss	0.0	0.0	0.0
Expected participant contributions	0.0	0.0	0.0
Total other pension and postretirement (benefit) cost, net	(7.3)	(9.9)	5.2
Net periodic pension and OPEB (benefit) cost	(3.7)	(6.6)	10.7
Consolidated
Defined Benefit Plan Disclosure [Line Items]
Service cost	3.7	4.2	6.8
Interest cost	150.5	162.9	120.0
Expected return on plan assets, net of expenses	(169.8)	(157.8)	(154.2)
Amortization of prior service (benefit) cost	(0.4)	(0.4)	(0.4)
Amortization of net actuarial (gain) loss	(9.3)	(14.6)	(4.6)
Curtailment, settlement or special termination benefit (gain) loss	34.0	0.0	2.9
Expected participant contributions	0.0	(0.3)	(0.3)
Total other pension and postretirement (benefit) cost, net	5.0	(10.2)	(36.6)
Net periodic pension and OPEB (benefit) cost	$ 8.7	$ (6.0)	$ (29.8)