Employee Retirement Plans and Postretirement Benefits Expected Benefit Payments (Details) $ in Millions	Dec. 31, 2020 USD ($)
Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	$ 327.1
2020	327.1
2021	327.9
2022	328.1
2023	329.5
2026-2030	1,643.8
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year, Low End of Range	43.0
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	43.4
2020	42.8
2021	42.2
2022	42.0
2023	41.2
2026-2030	200.2
Minimum | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year, High End of Range	$ 4.0