Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan, Plan Amendment [Abstract]
Contribution to pension and other postemployment benefit plans			$ 21.3
Future contributions to pension and other postemployment benefit plans	$ 5.7		5.7
Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Total net pension cost and other postretirement benefit cost	0.8	$ 2.9	2.1	$ 13.7
Other Postretirement Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Total net pension cost and other postretirement benefit cost	(3.0)	(2.9)	(8.9)	(8.6)
Direct Operating Costs and Selling General and Administrative | Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost (1)	0.4	1.2	5.7	9.2
Direct Operating Costs and Selling General and Administrative | Other Postretirement Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost (1)	0.0	0.0	0.0	0.1
Other, Net
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Curtailment gain (2)			(11.4)
Other, Net | Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost (2)	7.3	6.4	20.7	19.1
Expected return on plan assets (2)	(9.2)	(9.3)	(27.3)	(28.2)
Amortization of net loss (2)	2.4	5.9	16.1	17.4
Amortization of prior service credit (2)	(0.1)	(1.3)	(1.7)	(3.8)
Curtailment gain (2)	0.0	0.0	(11.4)	0.0
Other, Net | Other Postretirement Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost (2)	0.1	0.2	0.4	0.7
Amortization of net loss (2)	0.2	0.2	0.6	0.5
Amortization of prior service credit (2)	$ (3.3)	$ (3.3)	(9.9)	$ (9.9)
Income Taxes [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Provision (benefit) for income tax in Defined Benefit Plan Curtailment			(1.4)
Income Taxes [Member] | Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Provision (benefit) for income tax in Defined Benefit Plan Curtailment			(1.4)
Other Current Liabilities [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			(1.6)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement			(29.9)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment			0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) for Plan Amendment			(31.5)
Accumulated Other Comprehensive Income (Loss) [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			1.3
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement			23.6
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment			(9.0)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) for Plan Amendment			15.9
Other Noncurrent Liabilities [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment			0.3
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement			6.3
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment			(1.0)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) for Plan Amendment			$ 5.6