Intangible Asset - Additional Information (Detail) £ in Millions, $ in Millions			3 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2019 GBP (£)	Mar. 31, 2020
Finite Lived Intangible Assets [Line Items]
Intangible asset estimated weighted- average remaining useful life			10 years 3 months 18 days
Food and Drug Administration
Finite Lived Intangible Assets [Line Items]
Milestone payment achieved | £		£ 5
Increase in intangible assets | $	$ 8.5