Pension and Other Post-Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Accumulative other comprehensive loss:
After-tax amount recognized in accumulated other comprehensive loss	$ 84.4		$ 84.4		$ 85.8	$ 87.1
Defined Benefit Pension [Member]
Change in Benefit Obligation
Service cost	1.7	$ 1.4	3.3	$ 3.0
Accumulative other comprehensive loss:
Defined Benefit Plan, Interest Cost	3.9	4.0	7.7	7.9
Defined Benefit Plan, Expected Return on Plan Assets	(6.0)	(6.5)	(12.0)	(13.0)
Defined Benefit Plan, Settlements, Benefit Obligation	0.1		0.1
Defined Benefit Plan, Net Periodic Benefit Cost	2.1	1.1	3.8	2.5
Unrecognized prior service credit	0.0	(0.3)	0.0	(0.5)
Defined Benefit Plan, Amortization of Gains (Losses)	2.4	2.5	4.7	5.1
Other Postretirement Benefit Plan [Member]
Change in Benefit Obligation
Service cost	0.1	0.1	0.1	0.1
Accumulative other comprehensive loss:
Defined Benefit Plan, Interest Cost	0.3	0.2	0.5	0.5
Defined Benefit Plan, Expected Return on Plan Assets	0.0	0.0	0.0	0.0
Defined Benefit Plan, Net Periodic Benefit Cost	0.2	0.1	0.3	0.3
Unrecognized prior service credit	(0.1)	0.0	(0.1)	(0.1)
Defined Benefit Plan, Amortization of Gains (Losses)	$ (0.1)	$ (0.2)	$ (0.2)	$ (0.2)