Acquisitions (Asset Acquisitions) (Details) - USD ($) $ in Millions	1 Months Ended							3 Months Ended		6 Months Ended
	Jun. 30, 2020	May 31, 2020	Mar. 31, 2020	Sep. 30, 2019	Apr. 30, 2019	Mar. 31, 2019	Jan. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Business Acquisition [Line Items]
Acquired IPR&D Expense								$ 241.8	$ 25.0	$ 294.1	$ 161.9
Sitryx Therapeutics Limited
Business Acquisition [Line Items]
Acquired IPR&D Expense			$ 52.3
AbCellera Biologics Inc.
Business Acquisition [Line Items]
Acquired IPR&D Expense		$ 25.0
Junshi Biosciences Co., Ltd.
Business Acquisition [Line Items]
Acquired IPR&D Expense		20.0
Undisclosed
Business Acquisition [Line Items]
Acquired IPR&D Expense		$ 174.8
Evox Therapeutics Ltd.
Business Acquisition [Line Items]
Acquired IPR&D Expense	$ 22.0
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
Avidity Biosciences, Inc.
Business Acquisition [Line Items]
Acquired IPR&D Expense					$ 25.0