Pension and Other Post-Retirement Benefits - Expected Benefit Plan Payments (Details) $ in Millions	Dec. 31, 2018 USD ($)
Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	$ 28.3
2019	27.6
2020	27.5
2021	27.5
2022	27.8
Years 2024-2028	137.2
Total	275.9
Nonqualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	2.5
2019	2.8
2020	2.6
2021	2.9
2022	3.0
Years 2024-2028	14.9
Total	28.7
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2018	3.2
2019	3.0
2020	2.8
2021	2.6
2022	2.4
Years 2024-2028	9.5
Total	$ 23.5