Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 5.3us-gaap_UnrecognizedTaxBenefits	$ 4.4us-gaap_UnrecognizedTaxBenefits	$ 15.1us-gaap_UnrecognizedTaxBenefits
Additions: Tax positions of current years	0.3	0.3	0.3
Additions: Tax positions of prior years	0.1	1.1	0.6
Reductions: Tax positions of prior years	(1.9)	(0.4)	(11.3)
Reductions: Settlements with taxing authorities	(1.3)	0	(0.2)
Reductions: Lapse of statute of limitations	(0.4)	(0.1)	(0.1)
Unrecognized tax benefits, ending balance	2.1us-gaap_UnrecognizedTaxBenefits	5.3us-gaap_UnrecognizedTaxBenefits	4.4us-gaap_UnrecognizedTaxBenefits
Reduction related to prior year tax position	1.9	0.4	11.3
Unrecognized tax benefits that reduced income tax expense but were offset by increase of valuation allowance			10.5
Unrecognized tax benefits that would impact effective tax rate	1.7
Interest and penalties recorded (benefit) expense	0.4	0.8	(1.3)
Interest and penalties accrued	$ 0.2	$ 1.1	$ 0.3

Unrecognized Tax Benefits that Reduced Income Tax Expenses but was Offset by Increase of Valuation Allowance

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- Definition

Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

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-Publisher FASB

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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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-Publisher FASB

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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