Shareholders' Equity, IPO and Impact of Corporate Reorganization (Details) $ / shares in Units, $ in Millions				1 Months Ended	12 Months Ended
	Feb. 09, 2021 USD ($) shares	Feb. 01, 2021 £ / shares shares	Jan. 22, 2021 $ / shares shares	Jul. 31, 2022 £ / shares shares	Dec. 31, 2022 £ / shares shares	Dec. 31, 2021 shares	Dec. 31, 2023 £ / shares	Feb. 09, 2021 £ / shares	Feb. 09, 2021 $ / shares
Stockholders Equity [Abstract]
Ordinary share of nominal value (in pounds per share) | £ / shares					£ 0.002		£ 0.002
Percentage of valuation used for redemption							150.00%
Number of shares cancelled (in shares)			6,414,412
Stock Options [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Initial Public Offering and Concurrent Private Placement [Member]
Stockholders Equity [Abstract]
Net proceeds after deductions for underwriting discounts, commissions and other expenses | $	$ 286.9
American Depositary Shares [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)				2,000,000
Ordinary share of nominal value (in pounds per share) | £ / shares				£ 0.002
American Depositary Shares [Member] | IPO [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)	11,426,280
Ordinary share of nominal value (in pounds per share) | £ / shares								£ 0.002
American Depositary Shares [Member] | Private Placement [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)	576,923
Ordinary share of nominal value (in pounds per share) | £ / shares								0.002
Share price at grant date (in dollars per share) | $ / shares									$ 26
Series A Preferred Stock [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Shares issued, per share (in pounds per share) | $ / shares			$ 0.01
Stock conversion ratio			1
Series B Preferred Stock [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Shares issued, per share (in pounds per share) | $ / shares			$ 0.01
Stock conversion ratio			1
Series C Preferred Stock [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Shares issued, per share (in pounds per share) | $ / shares			$ 0.01
Stock conversion ratio			1
Growth Shares [Member]
Stockholders Equity [Abstract]
Stock conversion ratio		1
Number of shares converted (in shares)		6,250,000
Growth Shares [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Shares issued, per share (in pounds per share) | $ / shares			$ 0.01
Non-voting Ordinary Shares [Member]
Stockholders Equity [Abstract]
Ordinary share of nominal value (in pounds per share) | £ / shares				£ 0.002
Number of shares before re-designation (in shares)		20
Number of shares before re-designation (in pounds per share) | £ / shares		£ 0.0001
Number of shares after re-designation (in shares)		1
Number of shares after re-designation (in pounds per share) | £ / shares		£ 0.002
Ordinary Shares [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)					3,733,333	12,003,203
Number of shares before re-designation (in shares)		20
Number of shares before re-designation (in pounds per share) | £ / shares		£ 0.0001
Number of shares after re-designation (in shares)		1
Number of shares after re-designation (in pounds per share) | £ / shares		£ 0.002
Ordinary Shares [Member] | Immunocore Limited [Member]
Stockholders Equity [Abstract]
Exchange ratio			100
Shares issued, per share (in pounds per share) | $ / shares			$ 0.01
Ordinary Shares [Member] | IPO [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)	11,426,280
Ordinary share of nominal value (in pounds per share) | £ / shares								0.002
Ordinary Shares [Member] | Private Placement [Member]
Stockholders Equity [Abstract]
Number of shares issued (in shares)	576,923
Ordinary share of nominal value (in pounds per share) | £ / shares								£ 0.002
Ordinary Shares [Member] | Growth Shares [Member]
Stockholders Equity [Abstract]
Number of shares converted (in shares)		1,926,000
Ordinary Shares [Member] | Non-voting Ordinary Shares [Member]
Stockholders Equity [Abstract]
Number of shares converted (in shares)		16,632,540
Deferred Shares [Member] | Growth Shares [Member]
Stockholders Equity [Abstract]
Stock conversion ratio		3
Number of shares converted (in shares)		4,324,000