Pension and Other Postretirement Benefits (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 0.6	$ 0.9	$ 1.2	$ 1.8
Interest cost	8.4	9.6	16.8	19.5
Expected return on plan assets	(10.9)	(10.7)	(21.8)	(21.5)
Amortization of prior service cost	(0.7)	(0.6)	(1.4)	(1.3)
Recognized actuarial (gain) loss	5.0	5.3	9.9	10.7
Net periodic benefit cost (gain)	2.4	4.5	4.7	9.2
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Interest cost	0.9	1.2	1.8	2.4
Amortization of prior service cost	(0.5)	(0.5)	(1.0)	(1.0)
Recognized actuarial (gain) loss	(0.8)	(0.5)	(1.6)	(1.0)
Net periodic benefit cost (gain)	$ (0.4)	$ 0.2	$ (0.8)	$ 0.4