Employee Benefits, Net Periodic Benefit Costs and Charges Relating To Other Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-cash net periodic benefit income	$ 6.6	$ 4.8	$ 3.7
Defined contribution plans	8.8	8.9	8.9
Deferred Compensation Arrangement with Individual, Compensation Expense	1.0	1.8	0.9
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement	0.0	0.0	(0.1)
Other expenses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-cash net periodic benefit income	21.0	20.1	18.1
VEBAs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-cash net periodic benefit income	6.1	4.5	3.4
VEBAs | All Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-cash net periodic benefit income	$ 6.1	$ 4.5	$ 3.4