Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Aug. 10, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Plan Amendment [Abstract]
Net changes in pension and other postretirement plan assets and benefit obligations recognized in other comprehensive income, net of income tax expense of $10.3 for the three and nine months ended September 30, 2016 (See Note 3).		$ 0.0	$ 19.2	$ 0.0	$ 19.2
Contribution to pension and other postemployment benefit plans				25.9
Future contributions to pension and other postemployment benefit plans				6.1
Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost		1.2	4.6	9.2	12.2
Interest cost		6.4	6.7	19.1	19.7
Expected return on plan assets		(9.3)	(9.9)	(28.2)	(29.7)
Amortization of net loss		5.9	5.6	17.4	15.8
Amortization of prior service credit		(1.3)	(1.2)	(3.8)	(3.7)
Total net pension cost and other postretirement benefit cost		2.9	5.8	13.7	14.3
Other Postretirement Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost		0.0	0.0	0.1	0.2
Interest cost		0.2	0.4	0.7	1.4
Amortization of net loss		0.2	0.2	0.5	0.2
Amortization of prior service credit		(3.3)	(2.9)	(9.9)	(3.1)
Total net pension cost and other postretirement benefit cost		$ (2.9)	$ (2.3)	$ (8.6)	$ (1.3)
Defined Benefit Plan, Plan Amendment [Abstract]
Increase (Decrease) In Postretirement Benefits Plan Liability	$ (29.5)
Net changes in pension and other postretirement plan assets and benefit obligations recognized in other comprehensive income, net of income tax expense of $10.3 for the three and nine months ended September 30, 2016 (See Note 3).	19.2
Increase (Decrease) in Deferred Income Taxes	10.3
Accumulated other comprehensive income (loss) [Member] | Other Postretirement Benefit [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Plan Amendments	25.9
Defined Benefit Plan, Other Changes	(3.4)
Defined Benefit Plan, Actuarial Gain (Loss)	(3.3)
Deferred Tax Liability [Member] | Other Postretirement Benefit [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Plan Amendments	14.0
Defined Benefit Plan, Other Changes	(1.8)
Defined Benefit Plan, Actuarial Gain (Loss)	(1.9)
Other Liabilities [Member] | Other Postretirement Benefit [Member]
Defined Benefit Plan, Plan Amendment [Abstract]
Defined Benefit Plan, Plan Amendments	(39.9)
Defined Benefit Plan, Other Changes	5.2
Defined Benefit Plan, Actuarial Gain (Loss)	$ 5.2