Fair Value Measurement (Qualitative Information About Liabilities Measured at Fair Value on Recurring Basis Using Level 3 Inputs) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Joint venture net written option	$ 56.4	$ 11.5
Recurring Basis | Contingent Consideration Payable | Income approach (probability weighted discounted cash flow)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Liabilities	$ 1,209.2
Recurring Basis | Derivative Financial Instruments, Liabilities
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Cash flow scenario probability weighting	100.00%
Assumed market participant discount rate	14.00%
Minimum | Recurring Basis | Contingent Consideration Payable
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Cumulative probability of milestones being achieved (in percent)	10.00%
Assumed market participant discount rate	2.30%
Periods in which milestones are expected to be achieved	2018
Forecast quarterly royalties payable on net sales of relevant products	$ 0.1
Maximum | Recurring Basis | Contingent Consideration Payable
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Cumulative probability of milestones being achieved (in percent)	95.00%
Assumed market participant discount rate	8.90%
Periods in which milestones are expected to be achieved	2040
Forecast quarterly royalties payable on net sales of relevant products	$ 6.5
Fair value | Recurring Basis
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Joint venture net written option	$ 37.0	$ 40.0