Adaptimmune Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Underwritten public offering and Registered direct offering (Details)

Stockholders' equity - Underwritten public offering and Registered direct offering (Details) - USD ($)				12 Months Ended
	Sep. 07, 2017	Apr. 10, 2017	Mar. 27, 2017	Dec. 31, 2018	Dec. 31, 2017
Stockholders' equity
Proceeds from issuance of common stock				$ 99,653,000	$ 103,167,000
Common stock
Stockholders' equity
Issuance of common stock (in shares)					136,201,338
Stock offering expenses				$ 347,000	$ 4,774,000
Underwritten public offering
Stockholders' equity
Issuance of shares represented by American Depositary Shares (in ADSs)			15,700,223
Share price per ADS (in dollars per share)			$ 4.20
Underwritten public offering \| Common stock
Stockholders' equity
Issuance of common stock (in shares)			94,201,338
Proceeds from issuance of common stock			$ 61,397,000
Stock offering expenses			$ 4,544,000
Matrix Capital Management Company, LP
Stockholders' equity
Issuance of shares represented by American Depositary Shares (in ADSs)		7,000,000
Share price per ADS (in dollars per share)		$ 6.00
Matrix Capital Management Company, LP \| Common stock
Stockholders' equity
Issuance of common stock (in shares)		42,000,000
Proceeds from issuance of common stock		$ 41,770,000
Stock offering expenses		$ 230,000
Matrix Capital Management Company L P, New Enterprise Associates 16, L.P. New Enterprise Associates 14, L.P. and Syncona Portfolio Limited
Stockholders' equity
Issuance of shares represented by American Depositary Shares (in ADSs)	10,000,000
Share price per ADS (in dollars per share)	$ 10.00
Matrix Capital Management Company L P, New Enterprise Associates 16, L.P. New Enterprise Associates 14, L.P. and Syncona Portfolio Limited \| Common stock
Stockholders' equity
Issuance of common stock (in shares)	60,000,000
Proceeds from issuance of common stock	$ 99,653,000
Stock offering expenses	$ 347,000