Benefits (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Pension Plans, Defined Benefit [Member]	Jun. 30, 2011 Pension Plans, Defined Benefit [Member]	Jun. 30, 2012 Pension Plans, Defined Benefit [Member]	Jun. 30, 2011 Pension Plans, Defined Benefit [Member]	Jun. 30, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Jun. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]	Jun. 30, 2012 Other Postretirement Benefit Plans, Defined Benefit [Member]	Jun. 30, 2011 Other Postretirement Benefit Plans, Defined Benefit [Member]
Net Periodic Benefit Cost
Service cost				$ 5.4	$ 3.3	$ 10.8	$ 7.9	$ 2.4	$ 2.4	$ 5.2	$ 5.2
Interest cost				16.4	17.1	32.8	33.8	5.1	5.1	10.2	10.4
Expected return on plan assets				(22.2)	(20.4)	(44.8)	(41.1)	(4.8)	(4.1)	(9.6)	(8.4)
Amortization of:
Transition obligation								0.1	0.1	0.2	0.2
Prior service cost (credit)				0.6	0.5	1.2	1.1	(0.4)	(0.5)	(0.9)	(1.0)
Actuarial loss				10.3	9.0	20.2	17.1	1.7	1.5	3.5	3.0
Net Periodic Benefit Cost				10.5	9.5	20.2	18.8	4.1	4.5	8.6	9.4
Benefits (Textuals) [Abstract]
Pension and Other Postretirement Benefit Contributions	0	122.4
Estimated liability of Postemployment benefits	$ 5.2		$ 15.3