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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 |  |

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- Definition Milestone payment received. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Remaining amortization period of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 926 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54445-107959 + Details
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- Definition The increase (decrease) during the reporting period in intangible assets (for example patents and licenses). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details
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