Employee Benefits - Benefit Obligations and Funded Status of Pension Plans, OPEB and Salaried VEBAs (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (83.5)
Other Postretirement Benefits Plan | Long term Liabilities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan	81.9
Other Postretirement Benefits Plan | Current Liabilities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan	1.6
Salaried VEBA
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss) due to change in discount rate	3.0	$ (5.7)
Actuarial gain due to changes in census data	3.9	1.0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (20.6)	$ (17.8)