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