Quarterly report pursuant to Section 13 or 15(d)

Collaboration and Research Arrangements - Additional Information (Details)

Collaboration and Research Arrangements - Additional Information (Details) - USD ($)			1 Months Ended		3 Months Ended		9 Months Ended
	Dec. 17, 2019	Jan. 08, 2018	Nov. 30, 2019	Jan. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 25,395,000		$ 25,395,000		$ 28,378,000
Deferred revenue, net of current portion					14,218,000		14,218,000		22,639,000
GBT
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					17,882,000		17,882,000		20,000,000
GBT \| Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial period of research term	3 years
Additional extension period for research term upon mutual agreement	1 year
Upfront payment receivable	$ 20,000,000.0
Reimbursements receivable of full-time employee and out-of-pocket costs and expenses	$ 40,000,000.0
Agreement termination, prior written notice if notice delivered during the research term	9 months
Agreement termination, prior written notice if notice delivered after the expiration or termination of the research term	90 days
Total transaction price	$ 60,000,000.0						60,000,000.0
Upfront non-refundable and non-creditable payment	20,000,000.0
Reimbursable costs	$ 40,000,000.0
Change in total transaction price							0
Revenue recognized					3,500,000		8,200,000
Deferred revenue					17,900,000		17,900,000
Deferred revenue, short-term					7,800,000		7,800,000
Deferred revenue, net of current portion					10,100,000		10,100,000
GBT \| Collaboration Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Period of extension of initial research term	2 years
Receivable from option exercise, development, regulatory, commercialization and sales-based milestones per product candidate and product resulting	$ 315,000,000.0
Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized					300,000	$ 600,000	1,200,000	$ 1,500,000
Deferred revenue					7,513,000		7,513,000		$ 8,378,000
Deferred revenue, short-term					3,400,000		3,400,000
Deferred revenue, net of current portion					$ 4,100,000		4,100,000
Incyte \| Stock Purchase Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate purchase price				$ 10,000,000.0
Shares issued				793,021
Share price (in dollars per share)				$ 12.61
Premium to volume-weighted sale price of shares (as a percent)				30.00%
Trading days within which the purchase price represents a thirty percent (30%) premium to the volume-weighted sale price of the shares				15 days
Incyte \| Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total transaction price		$ 12,300,000	$ 12,800,000				12,800,000
Upfront non-refundable and non-creditable payment							2,500,000
Up-front consideration				$ 10,000,000.0
Up-front consideration, cash				2,500,000
Up-front consideration, pre-paid research funding				$ 7,500,000
Prepaid research amount							7,500,000
Premium paid on equity investment							2,300,000
Collaboration agreement additional consideration incurred							$ 500,000