Pension and Other Postretirement Benefits (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	$ 0.6	$ 0.7	$ 1.8	$ 2.5
Interest cost	8.4	9.1	25.2	28.6
Expected return on plan assets	(10.9)	(10.6)	(32.7)	(32.1)
Amortization of prior service cost	(0.6)	(0.7)	(2.0)	(2.0)
Recognized actuarial (gain) loss	5.4	5.2	15.3	15.9
Net periodic benefit cost (gain)	2.9	3.7	7.6	12.9
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Interest cost	0.9	1.1	2.7	3.5
Amortization of prior service cost	(0.5)	(0.5)	(1.5)	(1.5)
Recognized actuarial (gain) loss	(0.8)	(0.5)	(2.4)	(1.5)
Net periodic benefit cost (gain)	$ (0.4)	$ 0.1	$ (1.2)	$ 0.5