Collaboration and License Agreements - Celegene Purchase Agreements (Details)	1 Months Ended
	May 31, 2016 USD ($) extension	Sep. 30, 2019 USD ($)	May 17, 2016 USD ($)
2010 Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received		$ 80,000,000.0
Milestone payments upon achievement of specified regulatory milestone events		55,000,000.0
Milestone payment upon achievement of a specified commercial milestone event		$ 25,000,000.0
2016 Agreement | Celgene
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of agreements	4 years
Extension period | extension	2
Number of allowable special case extensions | extension	4
Special case extension term	1 year
Upfront payment agreement extension fee receivable	$ 40,000,000.0
Option exercise fee receivable			$ 30,000,000.0
2016 Agreement | Celgene | Specified clinical development event
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	20,000,000.0
2016 Agreement | Celgene | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	168,800,000
2016 Agreement | Celgene | Maximum | Specified regulatory milestone events
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	$ 148,800,000