Income Taxes (Unrecognized Tax Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits at January 1	$ 45.3	$ 30.6
Increases related to: tax positions taken during a prior period	11.8	17.3
Increases related to: tax positions taken during the current period	0.4	0.4
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	0.0	0.0
Decreases related to: lapse of applicable statute of limitations	(0.7)	(3.0)
Decreases related to: settlements with taxing authorities	0.0	0.0
Unrecognized tax benefits at December 31	$ 56.8	$ 45.3

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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