Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Income Taxes [Line Items]
Unrecognized tax benefits	$ 843.3
Unrecognized tax benefits that would have a favorable impact	740.2
Decrease in unrecognized tax benefits reasonable possible amount	185.0
Decrease in unrecognized tax benefits, amount of positive impact on effective tax rate	$ 75.0
Domestic Tax Authority
Income Taxes [Line Items]
Income tax rate	19.00%

Decrease in Unrecognized Tax Benefits is Reasonably Possible, Amount Positive Impact on Effective Tax Rate

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[Line Items] for Income Taxes [Table]

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Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

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

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Amount of unrecognized tax benefits.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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