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Intangible Asset - Additional Information (Detail)
£ in Millions, $ in Millions
9 Months Ended
Dec. 31, 2019
USD ($)
Dec. 31, 2019
GBP (£)
Sep. 30, 2020
Finite Lived Intangible Assets [Line Items]      
Intangible asset estimated weighted- average remaining useful life     9 years 9 months 18 days
Milestone payment achieved | £   £ 5  
Increase in intangible assets | $ $ 8.5