v3.26.1
EARNINGS PER SHARE (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Numerator:        
Net income attributable to equity holders of Constellium SE $ 146 $ 36 $ 345 $ 73
Denominator:        
Basic - weighted-average ordinary shares outstanding (in shares) 135,866,171 140,820,828 135,633,294 141,665,123
Dilutive effect of non-vested restricted stock units and performance-based restricted stock units (in shares) 4,287,582 1,423,571 4,488,781 1,508,801
Diluted - weighted-average ordinary shares, of restricted stock units and performance-based restricted stock units (in shares) 140,153,753 142,244,399 140,122,075 143,173,924
Basic earnings per share (in USD per share) $ 1.07 $ 0.25 $ 2.54 $ 0.51
Diluted earnings per share (in USD per share) $ 1.04 $ 0.25 $ 2.46 $ 0.51
Antidilutive securities excluded from computation of earnings per share (in shares) 0 0 0 0