Income Taxes (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Income Taxes (Textual)
Provision for income tax expense (benefit)	$ 18.1	$ (0.4)	$ 21.9	$ 0.7
Income tax expense	16.0	1.6	50.0	5.9
Estimated effective federal and state income tax rate	40.00%		40.00%
Income Tax Benefit Resulting from Settlement of Federal Income Tax Claims	24		24
Income Tax Benefit Resulting from Reduction in Unrecognized Tax Benefits	2.0	2.3	8.0	7.6
Reduction in Valuation Allowance			8		825
Valuation Allowance	105		105		113
Value of net deferred tax assets included in the condensed consolidated balance sheet	649.6		649.6
Value of net deferred tax assets included in other current assets	27.1		27.1
Deferred Income Tax Expense		0.3	23.4	2.4
Remaining gross unrecognized tax benefits	8.0		8.0		12.6
Accrued interest expense related to unrecognized tax benefits	0.1		0.1		1.1
Net Interest Income (Expense) as Part of Our Income Tax Provision	1.2	0.5	3.0	2.3
Total accrued interest income	0		0		0.3
Cumulative changes in ownership interests of significant shareholders			over three-year period in excess of 50%
Reductions to unrecognized tax benefits as result of a lapse of the applicable statute of limitations, gross unrecognized income tax benefits			(3.2)
Estimated income tax expense associated with federal income tax on state income tax refunds received	$ 4		$ 4
Possible Decrease in Unrecognized Tax Benefits, Time Period			12 months
Time period for cumulative changes in ownership interests of significant shareholders			3 years
Minimum cumulative changes in ownership interests of significant shareholders			50.00%