Pension and Other Postemployment Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]
Components of net periodic expense of Pension and OPEB plans
Service cost	$ 0.2	$ 0.6	$ 0.7	$ 1.7
Interest cost	1.7	1.7	5.3	5.1
Expected return on plan assets	(2.1)	(2.2)	(6.3)	(6.5)
Amortization of net loss (gain)	0.2	0.6	0.6	2.0
Amortization of unrecognized prior service (credit)	0	0	(0.1)	(0.1)
Net periodic expense (benefit)	0	0.7	0.2	2.2
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	(9.6)
Amortization of unrecognized prior service (credit)	0	(0.5)	0	(1.5)
Net periodic expense (benefit)	$ 0	$ (3.7)	$ 0	$ (11.1)