Income Taxes Effective tax rate (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate	85.00%	97.00%	(4.00%)	(66.00%)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%	35.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent			2.00%
Income Tax Expense (Benefit)			$ 5.7
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 1.6	$ 2.7	12.8	$ 12.6
Discretetaxbenefitcontingentconsiderationrevaluation	$ 4.4		$ 4.9

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Amount of other income tax expense (benefit).

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