Pension and Other Postemployment Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits [Member]
Components of net periodic expense of Pension and OPEB plans
Service cost	$ 0.2	$ 0.5	$ 0.5	$ 1.1
Interest cost	1.9	1.7	3.6	3.4
Expected return on plan assets	(2.1)	(2.1)	(4.2)	(4.3)
Amortization of net loss (gain)	0.1	0.7	0.4	1.4
Amortization of unrecognized prior service (credit)	0	(0.1)	(0.1)	(0.1)
Net periodic expense (benefit)	0.1	0.7	0.2	1.5
Other Benefits [Member]
Components of net periodic expense of Pension and OPEB plans
Service cost	0	0	0	0
Interest cost	0	0	0	0
Expected return on plan assets	0	0	0	0
Amortization of net loss (gain)	0	(3.2)	0	(6.4)
Amortization of unrecognized prior service (credit)	0	(0.5)	0	(1.0)
Net periodic expense (benefit)	$ 0	$ (3.7)	$ 0	$ (7.4)