Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Benefits (Textuals) [Abstract]
Pension and Other Postretirement Benefit Contributions	$ 0	$ 122.4	$ 122.4
Estimated liability of Postemployment benefits	5.2		15.3
Pension Plans, Defined Benefit [Member]
Net Periodic Benefit Cost
Service cost	5.4	4.6
Interest cost	16.4	16.7
Expected return on plan assets	(22.6)	(20.7)
Amortization of:
Prior service cost (credit)	0.6	0.6
Actuarial Loss	9.9	8.1
Net Periodic Benefit Cost	9.7	9.3
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net Periodic Benefit Cost
Service cost	2.8	2.8
Interest cost	5.1	5.3
Expected return on plan assets	(4.8)	(4.3)
Amortization of:
Transition obligation	0.1	0.1
Prior service cost (credit)	(0.5)	(0.5)
Actuarial Loss	1.8	1.5
Net Periodic Benefit Cost	$ 4.5	$ 4.9