Pension and Other Post-Retirement Benefits (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Defined Benefit Pension [Member]
Components of pension and other post retirement benefit costs
Service cost	$ 1.4	$ 1.2	$ 4.1	$ 4.0
Interest cost	5.2	5.6	15.6	16.6
Expected return on plan assets	(8.4)	(8.5)	(25.0)	(25.1)
Unrecognized prior service credit	(0.3)	(0.2)	(0.8)	(0.8)
Unrecognized net actuarial loss (gain)	1.8	1.1	5.4	4.5
Net costs	(0.3)	(0.8)	(0.7)	(0.8)
Retiree Health and Life [Member]
Components of pension and other post retirement benefit costs
Service cost	0.1	(0.1)	0.2	0.1
Interest cost	0.6	0.6	1.7	1.8
Unrecognized prior service credit		(0.1)	(0.1)	(0.1)
Unrecognized net actuarial loss (gain)	(0.1)	(0.2)	(0.2)	(0.2)
Net costs	$ 0.6	$ 0.2	$ 1.6	$ 1.6