Available borrowings under credit facility.

No definition available.

Name:	cstm_BorrowingFacility
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Disclosure of liquidity risk.

+ References

No definition available.

+ Details

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Namespace Prefix:	cstm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Total nominal amount of hedging instrument.

+ References

No definition available.

+ Details

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

- Definition

Revolving credit facility outstanding.

+ References

No definition available.

+ Details

Name:	cstm_RevolvingCreditFacilityOutstanding
Namespace Prefix:	cstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current derivative financial assets. [Refer: Derivative financial assets]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of financial assets held for managing liquidity risk (for example, financial assets that are readily saleable or expected to generate cash inflows to meet cash outflows on financial liabilities). [Refer: Liquidity risk [member]; Financial assets; Financial liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of undrawn borrowing facilities that may be available for future operating activities and to settle capital commitments. [Refer: Capital commitments]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Details

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- Details

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Balance Type:
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- Details

Name:	ifrs-full_BorrowingsByNameAxis=cstm_PanUSABLFacilityDueTwoThousandTwentySixMember
Namespace Prefix:
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Balance Type:
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- Details

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FINANCIAL RISK MANAGEMENT - Narrative (Details) $ in Millions	Jun. 30, 2022 EUR (€)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 EUR (€)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 EUR (€)	Dec. 31, 2020 EUR (€)
Disclosure of liquidity risk [line items]
Margin requirement	€ 46,000,000		€ 58,000,000
Revolving credit facilities outstanding availability	431,000,000
Liquidity value	899,000,000
Cash and cash equivalents	156,000,000		147,000,000		€ 290,000,000	€ 439,000,000
Undrawn facilities	743,000,000
Margin call
Disclosure of liquidity risk [line items]
Margin requirement	2,000,000		€ 0
Derivative classified as cash flow hedge
Disclosure of liquidity risk [line items]
Nominal amount hedging instrument \| $		$ 248		$ 274
U.S. Revolving Facility
Disclosure of liquidity risk [line items]
Borrowing base	€ 481,000,000	500
French Inventory Based Facility
Disclosure of liquidity risk [line items]
Borrowing base \| $		$ 100