Pension and Postretirement Benefit Costs (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Maximum [Member] | Non Qualified Pension Plans, Defined Benefit [Member]
Components of net periodic pension costs
Expected contribution to defined benefit pension plans	$ 2.0		$ 2.0
Pension Plans, Defined Benefit [Member]
Components of net periodic pension costs
Service cost for benefits earned	0.4	0.4	1.3	1.2
Interest cost on projected benefit obligation	12.4	12.6	37.3	37.8
Expected return on plan assets	(16.1)	(14.6)	(48.3)	(43.8)
Amortization of prior service cost	0.3	0.4	0.8	1.1
Amortization of actuarial loss	7.5	5.4	22.5	16.4
Net periodic pension costs	4.5	4.2	13.6	12.7
Qualified Pension Plans, Defined Benefit [Member]
Components of net periodic pension costs
Expected contribution to defined benefit pension plans	0		0
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic pension costs
Service cost for benefits earned	3.6	3.5	10.1	9.7
Interest cost on projected benefit obligation	14.5	14.7	43.4	43.8
Amortization of prior service cost	0.8	0.5	1.8	1.5
Amortization of actuarial loss	6.7	6.8	20.2	19.5
Net periodic pension costs	$ 25.6	$ 25.5	$ 75.5	$ 74.5