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Document and Entity Information
 6 Months Ended
Jun. 30, 2018
shares
Document - Document and Entity Information [Abstract]  
Document Type 6-K/A
Amendment Flag false
Document Period End Date Jun. 30, 2018
Document Fiscal Year Focus 2018
Document Fiscal Period Focus H1
Trading Symbol CSTM
Entity Registrant Name Constellium N.V.
Entity Central Index Key 0001563411
Current Fiscal Year End Date --12-31
Entity Common Stock, Shares Outstanding 0