Adaptimmune Quarterly report pursuant to Section 13 or 15(d)

Stockholders' equity - Underwritten public offering and Registered direct offering (Details) - USD ($)		3 Months Ended			6 Months Ended	9 Months Ended
	Aug. 10, 2021	Sep. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Stockholders' equity
Issue of shares under At The Market sales agreement, net of commission and expenses		$ 2,519,000
Remaining amount under the Sales Agreement						$ 197,360,000
Proceeds from issuance of common stock from offerings, net of commissions and issuance costs						$ 2,529,000	$ 334,388,000
Common stock
Stockholders' equity
Issue of shares under At The Market sales agreement, net of commission and expenses		$ 4,000
Issue of shares under At The Market sales agreement, net of commission and expenses, shares		3,069,330
Issuance of common stock (in shares)		3,069,330	141,450,000	144,900,000
American Depository Shares (ADSs)
Stockholders' equity
Issue of shares under At The Market sales agreement, net of commission and expenses, shares		511,555
Proceeds from issuance of common stock from offerings, net of commissions and issuance costs					$ 2,519,000
Maximum \| American Depository Shares (ADSs)
Stockholders' equity
Issue of shares under At The Market sales agreement, net of commission and expenses	$ 200,000,000