Pension and Other Post-Retirement Benefits (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Pension [Member]
Components of pension and other post retirement benefit costs
Service cost		$ 5.4	$ 5.3	$ 4.8
Interest cost		20.7	22.1	23.7
Expected return on plan assets		(33.2)	(33.5)	(31.2)
Unrecognized prior service credit	(1.0)	(1.0)	(1.0)	(1.0)
Unrecognized net actuarial loss (gain)	9.9	7.2	6.0	2.7
Net periodic (benefit) cost		(0.9)	(1.1)	(1.0)
Retiree Health and Life [Member]
Components of pension and other post retirement benefit costs
Service cost		0.2	0.2	0.2
Interest cost		2.2	2.4	2.9
Unrecognized prior service credit	(0.1)	(0.1)	(0.1)	(0.1)
Unrecognized net actuarial loss (gain)	(0.2)	(0.3)	(0.3)	(0.4)
Net periodic (benefit) cost		$ 2.0	$ 2.2	$ 2.6