Pension Benefits and Postretirement Benefits Other Than Pensions (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) employees	Jun. 30, 2017 USD ($)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Pension Plan, Number of Participants and Beneficiaries | employees			9,000
Defined Benefit Pension Plans, Number of Active Employees | employees			1,600
Service Cost	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Interest Cost on Projected Benefit Obligation	5.1	5.2	10.2	10.3
Expected Return on Plan Assets	(7.2)	(7.8)	(14.4)	(15.5)
Amortization of Accumulated Net Unrecognized Pension Costs	1.1	0.7	2.1	1.3
Total Expense (Benefit) Recognized	(1.0)	(1.9)	$ (2.1)	(3.9)
Postretirement Benefits Other than Pensions [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Postretirement Benefit Plan, Number of Retired Employees Covered | employees			475
Other Postretirement Benefit Plan, Number of Active Employees Covered | employees			200
Service Cost	0.1	0.1	$ 0.1	0.1
Interest Cost on Projected Benefit Obligation	0.1	0.1	0.2	0.2
Amortization of Prior Service Credit	(0.6)	(0.4)	(0.9)	(0.7)
Amortization of Accumulated Net Unrecognized Pension Costs	(0.3)	(0.5)	(0.7)	(0.9)
Total Expense (Benefit) Recognized	$ (0.7)	$ (0.7)	$ (1.3)	$ (1.3)