Collaborative Agreements and Acquisitions - Other In-License Agreements (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
Moderna Therapeutics, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement, up-front payment		$ 20.0
Collaborative arrangement, development and regulatory potential milestone payments maximum		$ 275.0
Arbor Biotechnologies, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement, up-front payment	$ 30.0
Collaborative arrangement, investment in collaborative partner, pursuant to convertible loan agreement	15.0
Collaborative arrangement, development and regulatory potential milestone payments maximum	$ 337.5