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, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Pension Plan, Defined Benefit [Member]	Jun. 30, 2012 Pension Plan, Defined Benefit [Member]	Jun. 30, 2013 Pension Plan, Defined Benefit [Member]	Jun. 30, 2012 Pension Plan, Defined Benefit [Member]	Jun. 30, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member]	Jun. 30, 2012 Other Postretirement Benefit Plan, Defined Benefit [Member]	Jun. 30, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member]	Jun. 30, 2012 Other Postretirement Benefit Plan, Defined Benefit [Member]
Net Periodic Benefit Cost
Service cost				$ 3.1	$ 5.4	$ 7.3	$ 10.8	$ 2.3	$ 2.4	$ 5.0	$ 5.2
Interest cost				15.1	16.4	30.2	32.8	3.9	5.1	7.8	10.2
Expected return on plan assets				(23.9)	(22.2)	(47.9)	(44.8)	(5.3)	(4.8)	(10.6)	(9.6)
Amortization of:
Transition obligation								0	0.1	0	0.2
Prior service cost (credit)				0.6	0.6	1.2	1.2	(0.5)	(0.4)	(1.0)	(0.9)
Actuarial loss				13.6	10.3	27.2	20.2	0.9	1.7	1.8	3.5
Net Periodic Benefit Cost				8.5	10.5	18.0	20.2	1.3	4.1	3.0	8.6
Benefits (Textuals) [Abstract]
Pension and Other Postretirement Benefit Contributions	0	0
Estimated liability of Postemployment benefits	$ 4.0		$ 4.0