Stock-Based Compensation (Intrinsic Value and Tax Deductions of Stock Appreciation Rights) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Realized tax benefits from tax deductions	$ 23.6	$ 0.0	$ 0.0
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeiture Rate	14.20%
Instrinsic value of stock appreciation rights exercised	$ 25.1	36.9	27.3
Realized tax benefits from tax deductions	$ 9.6	$ 14.1	$ 10.4

Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other Than Options Exercises in Period Intrinsic Value.

No definition available.

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- Definition

Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Forfeiture Rate.

+ References

No definition available.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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