Pension Benefits - Changes in Fair Value of Pension Plans Level 3 (Details) (Pension Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	$ 441.3
Transfers out of Level 3	(1.0)	1.0
Fair Value of Plan Assets at End of Year	457.6	441.3
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	41.4	45.2
Return on Plan Assets Still Held	1.8	1.7
Purchases, Sales and Settlements, Net	(14.7)	(6.5)
Fair Value of Plan Assets at End of Year	27.5	41.4
Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	1.0	0
Return on Plan Assets Still Held	0	0
Purchases, Sales and Settlements, Net	0	0
Transfers out of Level 3	(1.0)	1.0
Fair Value of Plan Assets at End of Year	0	1.0
Other Equity Interests [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	37.2	41.5
Return on Plan Assets Still Held	1.7	1.7
Purchases, Sales and Settlements, Net	(12.0)	(6.0)
Transfers out of Level 3	0	0
Fair Value of Plan Assets at End of Year	26.9	37.2
Receivables and Other [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at End of Year	3.1	6.1
Receivables and Other [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	3.2	3.7
Return on Plan Assets Still Held	0.1	0
Purchases, Sales and Settlements, Net	(2.7)	(0.5)
Transfers out of Level 3	0	0
Fair Value of Plan Assets at End of Year	$ 0.6	$ 3.2