Summary of Significant Accounting Policies - Segments (Details) - item	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Segment Information
Number of operating segments	1
Other customers
Segment Information
Percentages of revenue recognized	0.00%	0.00%
Royalty revenue \| Roche
Segment Information
Percentages of revenue recognized	98.00%
Royalty revenue \| Roche \| Revenues percentage
Segment Information
Percentages of revenue recognized		99.00%

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
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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
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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