| Cover - shares | 3 Months Ended | |
| Mar. 31, 2020 | May 13, 2020 | |
| Cover [Abstract] | ||
| Document Type | 10-Q/A | |
| Amendment Flag | false | |
| Document Quarterly Report | true | |
| Document Transition Report | false | |
| Document Period End Date | Mar. 31, 2020 | |
| Document Fiscal Period Focus | Q1 | |
| Document Fiscal Year Focus | 2020 | |
| Current Fiscal Year End Date | --12-31 | |
| Entity File Number | 001-37368 | |
| Entity Registrant Name | ADAPTIMMUNE THERAPEUTICS PLC | |
| Entity Central Index Key | 0001621227 | |
| Entity Tax Identification Number | 00-0000000 | |
| Entity Incorporation, State or Country Code | X0 | |
| Entity Address, Address Line One | 60 Jubilee Avenue | |
| Entity Address, Address Line Two | Milton Park | |
| Entity Address, City or Town | Abingdon, Oxfordshire | |
| Entity Address, Country | GB | |
| Entity Address, Postal Zip Code | OX14 4RX | |
| City Area Code | 44 | |
| Local Phone Number | 1235 430000 | |
| Title of 12(b) Security | American Depositary Shares, each representing 6 Ordinary Shares, par value £0.001 per share | |
| Trading Symbol | ADAP | |
| Security Exchange Name | NASDAQ | |
| Entity Current Reporting Status | Yes | |
| Entity Interactive Data Current | Yes | |
| Entity Filer Category | Accelerated Filer | |
| Entity Small Business | true | |
| Entity Emerging Growth Company | false | |
| Entity Shell Company | false | |
| Entity Common Stock, Shares Outstanding | 780,593,444 |
