Basis and Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Tax Cuts And Jobs Act Of 2017, Income tax expense (benefit)	$ (2.3)	$ (140.0)

Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit)

No definition available.

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