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
-Publisher FASB
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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Summary of Significant Accounting Policies - Concentration of Credit Risk and Significant Customers and Suppliers (Details) - Revenue - Customer concentration	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Combined BMS, Rockefeller and International AIDS Vaccine Initiative
Concentration risk
Concentration risk (as a percent)	86.00%	77.00%
Combined Rockefeller and BMS
Concentration risk
Concentration risk (as a percent)			71.00%