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Summary of Significant Accounting Policies - Summary of Collaborators that Represent More Than 10% of Accounts Receivable (Details) - Customer Concentration Risk - Accounts receivable	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Zai Lab Limited (Zai Lab)
Concentration Risk [Line Items]
Percentage of significant accounts receivable	76.00%	0.00%
Incyte Corporation (Incyte)
Concentration Risk [Line Items]
Percentage of significant accounts receivable	16.00%	0.00%
F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (Roche)
Concentration Risk [Line Items]
Percentage of significant accounts receivable	0.00%	73.00%
Les Laboratoires Servier and Institut de Recherches Servier (Servier)
Concentration Risk [Line Items]
Percentage of significant accounts receivable		12.00%

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