Summary of Significant Accounting Policies - Segments (Details) - item	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Segment Information
Number of operating segments	1
Roche
Segment Information
Percentages of revenue recognized	99.00%	37.00%
Takeda
Segment Information
Percentages of revenue recognized		56.00%

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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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