Collaboration Agreements - MERCK Composition of the Total Transaction Price (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 87,225
Decrease to the transaction price	7,100
Merck agreement 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	52,647	$ 59,735	$ 65,000
Decrease to the transaction price	(12,353)	(5,265)
Merck agreement 2015 \| Upfront payment
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	60,000	60,000	$ 60,000
Merck agreement 2015 \| Upfront Payment, Research And Development
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 5,000	$ 5,000

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in estimate of transaction price which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due. Includes, but is not limited to, change in assessment of whether estimate of variable consideration is constrained.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

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