Acquisitions (Asset Acquisitions) (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Jan. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Business Acquisition [Line Items]
Acquired IPR&D Expense				$ 52.3	$ 136.9
Sitryx Therapeutics Limited
Business Acquisition [Line Items]
Acquired IPR&D Expense				$ 52.3
AC Immune SA
Business Acquisition [Line Items]
Acquired IPR&D Expense	$ 30.2		$ 96.9
ImmuNext, Inc.
Business Acquisition [Line Items]
Acquired IPR&D Expense		$ 40.0