Collaborative Arrangements - Kymera and Other In-License Agreements (Details) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2019 USD ($) target	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Investment in collaborative partner, pursuant to convertible loan agreement		$ 63.3	$ 46.9	$ 8.7
Kymera Therapeutics
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payment	$ 50.0
Right to license, number of targets (up to) | target	6
Collaborative arrangement development and regulatory potential milestone payments maximum	$ 170.0
Investment in collaborative partner, pursuant to convertible loan agreement	$ 20.0
Molecular Templates, Inc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payment		$ 25.9
Arbor
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payment			$ 30.0