Collaborative Arrangements and Acquisitions - Merck KGaA (Details) - Merck KGaA $ in Millions	1 Months Ended
	Dec. 31, 2018 USD ($)	Jan. 31, 2017 USD ($) pre-clinical_stage_program clinical-stage_program development_program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Right to license, number of development programs | development_program		4
Right to license, number of clinical stage programs | clinical-stage_program		2
Number of pre-clinical stage programs | pre-clinical_stage_program		2
Collaborative arrangement, up-front payment | $	$ 65.0	$ 230.0