Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Contribution to pension and other postemployment benefit plans			$ 13.8
Future contributions to pension and other postemployment benefit plans			19.0
Defined Benefit Pension [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 4.0	$ 3.8	8.0	$ 7.6
Interest cost	6.4	6.5	12.7	13.0
Expected return on plan assets	(9.5)	(9.9)	(18.9)	(19.8)
Amortization of net loss	5.8	5.1	11.5	10.2
Amortization of prior service credit	(1.3)	(1.3)	(2.5)	(2.5)
Total net pension cost and other postretirement benefit cost	5.4	4.2	10.8	8.5
Other Postretirement Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.1	0.1	0.1	0.2
Interest cost	0.3	0.5	0.5	1.0
Amortization of net loss	0.1	0.0	0.3	0.0
Amortization of prior service credit	(3.3)	(0.1)	(6.6)	(0.2)
Total net pension cost and other postretirement benefit cost	$ (2.8)	$ 0.5	$ (5.7)	$ 1.0