Collaboration and Research Arrangements - Schedule of Change in Accounts Receivable, Contract Assets and Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Disaggregation Of Revenue [Line Items]
Accounts receivable and contract assets, Balance at Beginning of Period	$ 2,331
Accounts receivable and contract assets, Additions	5,019
Accounts receivable and contract assets, Deductions	(4,728)
Accounts receivable and contract assets, Balance at End of Period	2,622
Contract liabilities, Balance at Beginning of Period	22,086
Contract liabilities, Additions	71
Contract liabilities, Deduction	(2,205)
Contract liabilities, Balance at End of Period	19,952
Incyte
Disaggregation Of Revenue [Line Items]
Contract liabilities, Balance at Beginning of Period	5,365
Contract liabilities, Deduction	(809)
Contract liabilities, Balance at End of Period	4,556
Global Blood Therapeutics
Disaggregation Of Revenue [Line Items]
Contract liabilities, Balance at Beginning of Period	16,721
Contract liabilities, Additions	71
Contract liabilities, Deduction	(1,396)
Contract liabilities, Balance at End of Period	15,396
Billed receivables from collaboration partners
Disaggregation Of Revenue [Line Items]
Accounts receivable, Balance at Beginning of Period	7
Accounts receivable, Additions	2,397
Accounts receivable, Deduction	(2,404)
Unbilled receivables from collaboration partners
Disaggregation Of Revenue [Line Items]
Contract assets, Balance at Beginning of Period	2,324
Contract assets, Additions	2,622
Contract assets, Deduction	(2,324)
Contract assets, Balance at End of Period	$ 2,622