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Income Taxes (Details Textual) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2019 | Jun. 30, 2019
Income Tax Contingency [Line Items] |  |  |  |
Deferred tax assets, other |  |  |  | $ 856.7
Deferred tax liabilities, other |  |  |  | $ 685.3
Decrease in unrecognized tax benefits is reasonably possible |  |  | $ 75.0 |
Denmark Manufacturing Operations |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Tax expense on disposal group |  | $ 61.3 | $ 61.3 |
TECFIDERA |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Deferred tax assets, decrease in value | $ 1,324.0 | 1,324.0 |  |
Deferred tax liabilities, decrease in value | 1,268.0 | 1,268.0 |  |
Income tax expense associated with reductions in deferred tax assets and liabilities | $ 56.0 | $ 56.0 |  |

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