v3.25.1

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2024	Jun. 30, 2024
Cover [Abstract]
Document Type	10-K/A
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	001-35931
Entity Registrant Name	Constellium SE
Entity Central Index Key	0001563411
Entity Incorporation, State or Country Code	I0
Entity Tax Identification Number	98-0667516
Entity Address, Address Line One	300 East Lombard Street
Entity Address, Address Line Two	Suite 1710
Entity Address, City or Town	Baltimore,
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21202
Entity Address, Country	US
City Area Code	443
Local Phone Number	420-7861
Title of 12(b) Security	Ordinary Shares
Trading Symbol	CSTM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float		$ 2.7
Common Stock, Shares Issued	146,819,884
Entity Common Stock, Shares Outstanding	143,523,308
Auditor Name	PricewaterhouseCoopers
Auditor Location	Neuilly-sur-Seine, France
Auditor Firm ID	1347

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

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No definition available.

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- Definition

PCAOB issued Audit Firm Identifier

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 10-K
-Number 249
-Section 310

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 20-F
-Number 249
-Section 220
-Subsection f

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 40-F
-Number 249
-Section 240
-Subsection f

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Balance Type:	na
Period Type:	duration

- References

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Namespace Prefix:	dei_
Data Type:	dei:internationalNameItemType
Balance Type:	na
Period Type:	duration

- References

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Namespace Prefix:	dei_
Data Type:	dei:internationalNameItemType
Balance Type:	na
Period Type:	duration

- Definition

Area code of city

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No definition available.

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- Definition

Cover page.

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No definition available.

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- Definition

End date of current fiscal year in the format --MM-DD.

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No definition available.

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Balance Type:	na
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- Definition

Boolean flag that is true only for a form used as an annual report.

+ References

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Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates whether any of the financial statement period in the filing include a restatement due to error correction.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K
-Number 229
-Section 402
-Subsection w

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 10-K
-Number 249
-Section 310

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 20-F
-Number 249
-Section 220
-Subsection f

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form 40-F
-Number 249
-Section 240
-Subsection f

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- Definition

Fiscal period values are FY, Q1, Q2, and Q3. 1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY.

+ References

No definition available.

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Period Type:	duration

- Definition

This is focus fiscal year of the document report in YYYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006.

+ References

No definition available.

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- Definition

For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

+ References

No definition available.

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- Definition

Boolean flag that is true only for a form used as a transition report.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Forms 10-K, 10-Q, 20-F
-Number 240
-Section 13
-Subsection a-1

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Period Type:	duration

- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

+ References

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Address Line 1 such as Attn, Building Name, Street Name

+ References

No definition available.

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- Definition

Address Line 2 such as Street or Suite number

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No definition available.

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- Definition

Name of the City or Town

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No definition available.

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Period Type:	duration

- Definition

ISO 3166-1 alpha-2 country code.

+ References

No definition available.

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Namespace Prefix:	dei_
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Balance Type:	na
Period Type:	duration

- Definition

Code for the postal or zip code

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No definition available.

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Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Name of the state or province.

+ References

No definition available.

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Namespace Prefix:	dei_
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Balance Type:	na
Period Type:	duration

- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

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Namespace Prefix:	dei_
Data Type:	dei:centralIndexKeyItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	dei_
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Balance Type:	na
Period Type:	instant

- Definition

Indicate 'Yes' or 'No' whether registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. This information should be based on the registrant's current or most recent filing containing the related disclosure.

+ References

No definition available.

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Namespace Prefix:	dei_
Data Type:	dei:yesNoItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicate if registrant meets the emerging growth company criteria.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

+ References

No definition available.

+ Details

Name:	dei_EntityFileNumber
Namespace Prefix:	dei_
Data Type:	dei:fileNumberItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicate whether the registrant is one of the following: Large Accelerated Filer, Accelerated Filer, Non-accelerated Filer. Definitions of these categories are stated in Rule 12b-2 of the Exchange Act. This information should be based on the registrant's current or most recent filing containing the related disclosure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Balance Type:	na
Period Type:	duration

- Definition

Two-character EDGAR code representing the state or country of incorporation.

+ References

No definition available.

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Namespace Prefix:	dei_
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Balance Type:	na
Period Type:	duration

- Definition

Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-T
-Number 232
-Section 405

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Balance Type:	na
Period Type:	duration

- Definition

The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter.

+ References

No definition available.

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Namespace Prefix:	dei_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Balance Type:	na
Period Type:	duration

- Definition

Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates that the company is a Smaller Reporting Company (SRC).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Namespace Prefix:	dei_
Data Type:	dei:employerIdItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicate 'Yes' or 'No' if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.

+ References

No definition available.

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Namespace Prefix:	dei_
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Period Type:	duration

- Definition

Indicate 'Yes' or 'No' if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Is used on Form Type: 10-K, 10-Q, 8-K, 20-F, 6-K, 10-K/A, 10-Q/A, 20-F/A, 6-K/A, N-CSR, N-Q, N-1A.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Securities Act
-Number 230
-Section 405

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Namespace Prefix:	dei_
Data Type:	dei:yesNoItemType
Balance Type:	na
Period Type:	duration

- References

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Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Local phone number for entity.

+ References

No definition available.

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Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Title of a 12(b) registered security.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b

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Balance Type:	na
Period Type:	duration

- Definition

Name of the Exchange on which a security is registered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection d1-1

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- Definition

Trading symbol of an instrument as listed on an exchange.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

CONSTELLIUM SE 10-K/A