Pension and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 1.3	$ 1.3	$ 2.7	$ 2.7
Interest cost	4.3	4.5	8.6	9.0
Expected return on plan assets	(4.7)	(4.8)	(9.4)	(9.5)
Amortization of prior service cost	0.1	0.1	0.2	0.2
Amortization of net loss	2.1	1.7	4.3	3.5
Settlements or curtailments	6.3	0.2	6.3	1.6
Total net periodic pension cost	9.4	3.0	12.7	7.5
Other Benefits [Member]
Components of net periodic benefit cost
Service cost		0.2	0.3	0.4
Interest cost	0.1	0.3	0.3	0.5
Expected return on plan assets
Amortization of prior service cost	(0.8)	(0.5)	(1.3)	(1.0)
Amortization of net loss	0.4	0.3	0.7	0.6
Settlements or curtailments
Total net periodic pension cost	$ (0.3)	$ 0.3		$ 0.5