Pension and Postretirement Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 1.4	$ 1.4
Interest cost	4.3	4.5
Expected return on plan assets	(4.7)	(4.8)
Amortization of prior service cost	0.1	0.1
Amortization of net loss	2.2	1.7
Settlements and curtailments		1.5
Total net periodic pension cost	3.3	4.4
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0.3	0.2
Interest cost	0.2	0.2
Amortization of prior service cost	(0.5)	(0.5)
Amortization of net loss	0.3	0.3
Total net periodic pension cost	$ 0.3	$ 0.2