Earnings Per Share - Details of Earnings Per Share (Detail) € in Thousands	12 Months Ended
Dec. 31, 2025 $ / shares	Dec. 31, 2025 EUR (€) shares	Dec. 31, 2024 $ / shares	Dec. 31, 2024 EUR (€) shares	Dec. 31, 2023 $ / shares	Dec. 31, 2023 EUR (€) shares
Earnings per share [abstract]
Net income (loss) attributable to shareholders of Cellectis (in thousands) \| €		€ (67,593)		€ (36,761)		€ (101,059)
Net income (loss) attributable to shareholders of Cellectis from discontinued operations (in thousands) \| €		€ 0		€ 0		€ 15,776
Weighted average number of outstanding shares, used to calculate basic net result per share \| shares		100,279,276		90,566,346		57,012,815
Weighted average number of outstanding shares, net of effects of dilutive potential ordinary shares \| shares		100,279,276		90,566,346		57,012,815
Basic net income (loss) attributable to shareholders of Cellectis per share ( $ /share)	$ (0.67)		$ (0.41)		$ (1.77)
Diluted net income (loss) attributable to shareholders of Cellectis per share ( $ /share)	(0.67)		(0.41)		(1.77)
Basic net income (loss) attributable to shareholders of Cellectis from discontinued operations, per share ($ /share)	0		0		0.28
Diluted earnings from discontinued operations per share ( $ /share)	$ 0		$ 0		$ 0.28

The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

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Basic earnings (loss) per share from discontinued operations. [Refer: Basic earnings (loss) per share; Discontinued operations [member]]

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The profit (loss) attributable to ordinary equity holders of the parent entity. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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