Pension and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Benefits [Member]
Service cost - benefits earned during the period
Interest cost	7.9	8.1	15.8	16.3
Expected return on plan assets	(8.6)	(8.7)	(17.1)	(17.5)
Recognized net actuarial loss	3.7	4.2	7.5	8.4
Amortization of transition asset		(0.4)		(0.8)
Amortization of prior service cost
Net periodic cost (benefit)	3.0	3.2	6.2	6.4
Postretirement Benefits [Member]
Service cost - benefits earned during the period		0.1		0.1
Interest cost	0.6	0.6	1.2	1.3
Expected return on plan assets
Recognized net actuarial loss	0.1	0.1	0.2	0.2
Amortization of transition asset
Amortization of prior service cost	(1.3)	(1.5)	(2.6)	(2.9)
Net periodic cost (benefit)	$ (0.6)	$ (0.7)	$ (1.2)	$ (1.3)