Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	$ 5.9	$ 6.5	$ 11.8	$ 12.9
Expected return on plan assets	(6.8)	(6.8)	(13.7)	(13.6)
Recognized net actuarial loss	2.4	3.8	4.9	7.6
Net periodic pension cost (benefit)	1.5	3.5	3.0	6.9
Postretirement Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	0.1	0.1	0.2	0.2
Recognized net actuarial loss		0.1	0.1	0.1
Amortization of prior service cost	$ (0.1)	(0.4)	(0.2)	(0.7)
Net periodic pension cost (benefit)		$ (0.2)	$ 0.1	$ (0.4)