Summary of Percentage of Total Product Revenues (Detail)	3 Months Ended
Mar. 31, 2021
Disaggregation Of Revenue [Line Items]
Percentage of Product Revenues	100.00%
OncoMed Specialty LLC Onco360
Disaggregation Of Revenue [Line Items]
Percentage of Product Revenues	31.00%
Affiliates Of McKesson Corporation
Disaggregation Of Revenue [Line Items]
Percentage of Product Revenues	33.00%
Affiliates Of Amerisource Bergen Corporation
Disaggregation Of Revenue [Line Items]
Percentage of Product Revenues	23.00%
Affiliates Of Cardinal Health Specialty
Disaggregation Of Revenue [Line Items]
Percentage of Product Revenues	13.00%

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://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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