Income Taxes (Change in tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provisional income tax change	$ 289.5	$ 289.5
One time transition tax		431.2
Remeasurement of the company's taxes		134.5
Accrued taxes		65.1
Impacts partially offset by reversal of deferred tax liabilities		$ 341.3

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