Merck Arrangement - Additional Information (Detail 1) - Merck Sharp & Dohme Corp. [Member] $ in Millions	Apr. 30, 2019 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-05-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 9.5
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-05-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 3.4
Revenue, remaining performance obligation, expected timing of satisfaction, period	4 years