Employee Retirement Plans and Postretirement Benefits - Net Periodic Pension (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) pension_plan	Dec. 31, 2024 USD ($) pension_plan	Dec. 31, 2023 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 145.0	$ 150.5
Total other pension and postretirement (benefit) cost, net	$ (14.4)	$ 5.0	$ (10.2)
Purchased annuity contracts, number of Canadian pension plans | pension_plan	2	2
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.1	$ 0.1	0.9
Interest cost	124.0	129.7	140.4
Expected return on plan assets, net of expenses	(151.8)	(169.8)	(157.8)
Amortization of prior service (benefit) cost	0.4	0.3	0.3
Amortization of net actuarial (gain) loss	21.7	18.1	17.1
Curtailment, settlement or special termination benefit (gain) loss	(0.2)	34.0	0.0
Expected participant contributions	0.0	0.0	(0.3)
Total other pension and postretirement (benefit) cost, net	(5.9)	12.3	(0.3)
Net periodic pension and OPEB (benefit) cost	(5.8)	12.4	0.6
Pension | Canadian Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Curtailment, settlement or special termination benefit (gain) loss		34.0
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.5	3.6	3.3
Interest cost	21.0	20.8	22.5
Expected return on plan assets, net of expenses	0.0	0.0	0.0
Amortization of prior service (benefit) cost	(2.6)	(0.7)	(0.7)
Amortization of net actuarial (gain) loss	(27.0)	(27.4)	(31.7)
Curtailment, settlement or special termination benefit (gain) loss	0.1	0.0	0.0
Expected participant contributions	0.0	0.0	0.0
Total other pension and postretirement (benefit) cost, net	(8.5)	(7.3)	(9.9)
Net periodic pension and OPEB (benefit) cost	(6.0)	(3.7)	(6.6)
Consolidated
Defined Benefit Plan Disclosure [Line Items]
Service cost	2.6	3.7	4.2
Interest cost	145.0	150.5	162.9
Expected return on plan assets, net of expenses	(151.8)	(169.8)	(157.8)
Amortization of prior service (benefit) cost	(2.2)	(0.4)	(0.4)
Amortization of net actuarial (gain) loss	(5.3)	(9.3)	(14.6)
Curtailment, settlement or special termination benefit (gain) loss	(0.1)	34.0	0.0
Expected participant contributions	0.0	0.0	(0.3)
Total other pension and postretirement (benefit) cost, net	(14.4)	5.0	(10.2)
Net periodic pension and OPEB (benefit) cost	$ (11.8)	$ 8.7	$ (6.0)