Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1.6	$ 1.5	$ 4.9	$ 4.5
Interest cost	3.8	3.9	11.5	11.8
Expected return on plan assets	(5.9)	(6.5)	(17.9)	(19.5)
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0.0	(5.7)	(0.1)	(5.7)
Unrecognized prior service credit	0.0	(0.2)	0.0	(0.7)
Unrecognized net actuarial loss (gain)	2.2	2.6	6.9	7.7
Net expense	1.7	7.0	5.5	9.5
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	0.0	0.1	0.1	0.2
Interest cost	0.2	0.2	0.7	0.7
Expected return on plan assets	0.0	0.0	0.0	0.0
Unrecognized prior service credit	0.0	(0.1)	(0.1)	(0.2)
Unrecognized net actuarial loss (gain)	0.0	0.0	(0.2)	(0.2)
Net expense	$ 0.2	$ 0.2	$ 0.5	$ 0.5