Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Income Tax Contingency [Line Items]
Significant change in unrecognized tax benefits reasonably possible, amount of unrecognized tax positions that could be reduced	$ 3	$ 3
Unrecognized tax benefits decreases resulting from prior period tax positions	3.5	3.5
Unrecognized tax benefits for uncertain tax positions	128.7	128.7	139.8	99.9
Internal Revenue Service [Member]
Income Tax Contingency [Line Items]
Settlement of income tax matters	14.3	14.3
State [Member]
Income Tax Contingency [Line Items]
Settlement of income tax matters		2.9
A Single Uncertain Tax Position [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits for uncertain tax positions	$ 92.1	$ 92.1