For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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Summary of Significant Accounting Policies - Segments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Information
Number of operating segments	1
Other customers
Segment Information
Percentages of revenue recognized	0.00%
CytomX
Segment Information
Percentages of revenue recognized	13.00%	8.00%	13.00%
Debiopharm
Segment Information
Percentages of revenue recognized		2.00%	26.00%
Roche
Segment Information
Percentages of revenue recognized	64.00%	60.00%	24.00%
Sanofi
Segment Information
Percentages of revenue recognized			31.00%
Takeda
Segment Information
Percentages of revenue recognized		23.00%	4.00%
Jazz
Segment Information
Percentages of revenue recognized	18.00%