Acquisitions (Syntimmune) (Details) - Syntimmune, Inc [Member] - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2018	Dec. 31, 2018
Consideration
Upfront payment for acquisition of Syntimmune outstanding shares	$ 400.0
Asset Acquisition, Cash Acquired	4.2
Asset Acquisition, Working Capital Adjustment	2.3
Transaction costs	0.9
Total consideration	407.4
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Cash	4.2
Asset Acquisition, Recognized Identifiable Assets Acquired And Liabilities Assumed, In-Process Research And Development	375.2	$ 379.3
Deferred tax assets	25.1
Other assets and liabilities	2.9
Asset Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Assets	$ 407.4