Pension and Postretirement Benefit Plans (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 1.3	$ 1.3	$ 4.0	$ 3.7
Interest cost	4.5	4.4	13.5	13.2
Expected return on plan assets	(4.7)	(4.9)	(14.2)	(14.5)
Amortization of prior service cost	0.1	0.1	0.3	0.4
Amortization of net loss	1.7	2.1	5.2	6.4
Settlements or curtailments	0.1		1.7
Total net periodic pension cost	3.0	3.0	10.5	9.2
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0.2	0.2	0.6	0.4
Interest cost	0.2	0.2	0.7	0.6
Amortization of prior service cost	(0.4)	(0.5)	(1.4)	(1.4)
Amortization of net loss	0.3	0.3	0.9	0.9
Total net periodic pension cost	$ 0.3	$ 0.2	$ 0.8	$ 0.5