Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Valuation Allowance [Line Items]
Effective tax rate	0.40%	5.30%	7.20%	16.90%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	$ 23.3
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount				$ 46.1
Net unrecognized tax benefit	85.9		$ 85.9		$ 77.8
Income tax interest and penalties accrued	3.5		3.5
Deferred tax assets	$ 114.5		$ 114.5