Pension and Other Postemployment Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]
Components of net periodic expense of Pension and OPEB plans
Service cost	$ 0.3	$ 0.6
Interest cost	1.7	1.7
Expected return on plan assets	(2.1)	(2.2)
Amortization of net loss (gain)	0.3	0.7
Amortization of unrecognized prior service (credit)	(0.1)	0
Net periodic expense (benefit)	0.1	0.8
Other Benefits [Member]
Components of net periodic expense of Pension and OPEB plans
Service cost	0	0
Interest cost	0	0
Expected return on plan assets	0	0
Amortization of net loss (gain)	0	(3.2)
Amortization of unrecognized prior service (credit)	0	(0.5)
Net periodic expense (benefit)	$ 0	$ (3.7)