Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Income Taxes
Effective tax rate (as a percent)	38.60%	38.10%	37.00%	37.90%
Federal statutory rate (as a percent)			35.00%
Unrecognized tax benefit, if recognized, would affect the effective tax rate	$ 5.3		$ 5.3
Accrued interest recognized due to uncertain tax positions	0.9		0.9		0.8
Maximum reduction in unrecognized tax benefits due to expiration of statutes of limitation and audit settlements in next 12 months	$ 1.9		$ 1.9

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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- Definition

This element represents the amount of interest expense accrued as of the date of the statement of financial position for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

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