Pension and Other Postretirement Benefit Plans - Obligation and Funded Status (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Change in Plan Assets [Roll Forward]
Non-Current Liabilities	$ 228.2	$ 253.5
Other Investments, Grantor Trust	143.5	132.3
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation	598.7	550.6
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year	597.5	525.6
Service Cost	9.1	7.6	6.2
Interest Cost	26.4	27.4	26.2
Actuarial Loss (Gain)	38.5	54.6
Benefits Paid	(30.9)	(28.6)
Participant Contributions	11.5	10.9
Obligation, End of Year	652.1	597.5	525.6
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year	432.4	382.0
Actual Return on Plan Assets	38.7	33.2
Employer Contribution	19.9	45.8
Participant Contributions	11.5	10.9
Benefits Paid	(30.9)	(28.6)
Fair Value, End of Year	460.1	432.4	382.0
Funded Status, End of Year	(192.0)	(165.1)
Current Liabilities	(1.1)	(1.1)
Non-Current Liabilities	(190.9)	(164.0)
Postretirement Health and Life [Member]
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year	210.6	204.1
Service Cost	4.2	3.8	4.8
Interest Cost	9.4	10.8	10.9
Actuarial Loss (Gain)	(43.2)	(2.9)
Benefits Paid	(9.5)	(7.7)
Participant Contributions	2.6	2.5
Plan Amendments	(5.3)	0
Obligation, End of Year	168.8	210.6	204.1
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year	121.0	114.7
Actual Return on Plan Assets	14.3	0
Employer Contribution	2.3	11.4
Participant Contributions	2.6	2.5
Participant Contributions, Excluding Key Employees	2.5	2.5
Benefits Paid	(9.5)	(7.7)
Benefits Paid, Excluding Key Employees	(9.1)	(7.6)
Fair Value, End of Year	131.0	121.0	114.7
Funded Status, End of Year	(37.8)	(89.6)
Current Liabilities	(0.8)	(0.9)
Non-Current Liabilities	(37.0)	(88.7)
Grantor Trust [Member]
Change in Plan Assets [Roll Forward]
Other Investments, Grantor Trust	$ 22.1	$ 20.3