Pension and Other Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended		1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 31, 2012	Aug. 02, 2011	Jan. 31, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2011	Sep. 30, 2012	Sep. 30, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan contributions							$ 170.2	$ 170.0
Net periodic benefit cost (income) [Abstract]
Net periodic benefit cost (income)				(9.6)	(8.9)		(28.0)	(26.7)
Pension Plans, Defined Benefit [Member]
Net periodic benefit cost (income) [Abstract]
Service cost				0.8	0.8		2.4	2.4
Interest cost				40.1	45.1		120.2	135.5
Expected return on assets				(47.4)	(51.7)		(141.0)	(155.6)
Amortization of prior service cost (credit)				1.1	1.2		3.0	3.2
Amortization of (gain) loss				6.1	4.7		18.3	14.1
Net periodic benefit cost (income)				0.7	0.1		2.9	(0.4)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit cost (income) [Abstract]
Service cost				1.2	1.1		3.4	3.2
Interest cost				7.9	9.4		23.7	28.6
Amortization of prior service cost (credit)				(19.4)	(19.2)		(58.0)	(57.5)
Amortization of (gain) loss				0	(0.3)		0	(0.8)
Net periodic benefit cost (income)				(10.3)	(9.0)		(30.9)	(26.3)
Middletown Retirees [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit cost (income) [Abstract]
Settlement gain related to Middletown Retiree Settlement				0	0	(14.0)	0	(14.0)
Contributions to retirees VEBAs						65.0
Butler Works Retiree Healthcare Benefits Litigation [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Net periodic benefit cost (income) [Abstract]
Reversal of prior amortization related to Butler Retiree Settlement				0	0	14.2	0	14.2
Contributions to retirees VEBAs	31.7	21.4
Amount of combined lump sum payments to VEBA and plaintiff's counsel			91.0
Amount of cash contributions to the VEBA trust in the next year following the latest year				27.6			27.6
Increase in benefit obligation from litigation settlement						$ 29.6
Amortization Period On Remaining Portion Of Reversed Prior Amortization Recorded In Other Comprehensive Income In Number Of Years						5 years