Pensions and Other Postretirement Benefits (Components of OPEB Expense) (Details) (Other Benefits [Member], USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Other Benefits [Member]
Service cost	$ 2.3	$ 1.6	$ 4.7	$ 3.2
Interest cost	5.3	5.5	11.2	10.7
Expected return on plan assets	(3.7)	(3.3)	(8.0)	(6.5)
Prior service costs	0.2	0.5	0.8	0.9
Net actuarial loss	2.9	1.7	5.8	3.4
Net periodic benefit cost	7.0	6.0	14.5	11.7
Quarterly OPEB contributions			$ 21.9	$ 17.4