Provision for Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Provision for Income Taxes
Income tax provision	$ 12.4	$ 9.4	$ 15.0	$ 21.2
Effective tax rates (as a percent)	34.70%	48.70%	34.10%	45.90%
Unrecognized tax benefits	36.1		36.1		42.1
Portion of unrecognized tax benefits, which if recognized, would result in a reduction of the effective tax rate	17.5		17.5		23.6
Accrued interest and penalties related to uncertain tax positions	3.3		3.3		3.7
Penalties and interest expense relating to unrecognized tax benefits	$ (0.7)	$ 0.1	$ (0.4)	$ 0.2

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 sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized 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 and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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- Definition

This element represents the total of interest expense recognized 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 and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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