Shareholders's Equity (Schedule of Activity) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2018
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 8,088.8
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(188.0)	$ (140.5)
Other Comprehensive Income (Loss), Net of Tax	1.5	$ (0.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 7,900.3
Common Stock, Dividends, Per Share, Cash Paid	$ 0.04	$ 0.04
Common Stock [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Shares, Issued	115.2	111.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 46.2	$ 44.8
Shares, Issued	115.2	111.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 46.2	$ 44.8
Additional Paid-in Capital [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 7,225.0	$ 7,195.0
Shares Issued Under Share Based Compensation Plans, Shares	(0.1)	(0.1)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	$ 5.3	$ 7.5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	7,230.2	7,202.4
Retained Earnings [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	874.2	1,532.7
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(190.4)	(140.1)
Dividends, Common Stock, Cash	(4.5)	(4.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	679.3	1,387.4
Retained Earnings [Member] \| Accounting Standards Update 2018-02 [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ (0.8)
AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	18.2	28.6
Other Comprehensive Income (Loss), Net of Tax	1.5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	19.7	29.0
AOCI Attributable to Parent [Member] \| Accounting Standards Update 2018-02 [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 0.8
Treasury Stock [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (72.2)	$ (69.0)
Shares Issued Under Share Based Compensation Plans, Shares	0.1	0.1
Stock Repurchased During Period, Value	$ (2.8)	$ (1.1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(74.9)	(70.0)
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(2.6)	(2.1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2.4	(0.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (0.2)	$ (2.5)

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Amount of increase to additional paid-in capital (APIC) from recognition of equity-based compensation.

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Aggregate dividends paid during the period for each share of common stock outstanding.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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