Analysis of income and expense.

No definition available.

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

- Definition

Exchanges gains / (losses) from remeasurement of monetary assets and liabilities - net.

+ References

No definition available.

+ Details

Name:	cstm_ExchangesGainsLossesFromRemeasurementOfMonetaryAssetsAndLiabilitiesNet
Namespace Prefix:	cstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Realized gains (losses) on foreign currency derivatives - net.

+ References

No definition available.

+ Details

Name:	cstm_RealizedGainsLossesOnForeignCurrencyDerivativesNet
Namespace Prefix:	cstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Unrealized gains (losses) on foreign currency derivatives - net.

+ References

No definition available.

+ Details

Name:	cstm_UnrealizedGainsLossesOnForeignCurrencyDerivativesNet
Namespace Prefix:	cstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions, excluding those arising on financial instruments measured at fair value through profit or loss in accordance with IFRS 9. [Refer: At fair value [member]; Financial instruments, class [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 21
-IssueDate 2021-01-01
-Paragraph 52
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=21&code=ifrs-tx-2021-en-r&anchor=para_52_a&doctype=Standard
-URIDate 2021-03-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 35
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_35&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	cstm_ProfitAndLossStatementLocationAxis=cstm_RevenueFromContractWithCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cstm_ProfitAndLossStatementLocationAxis=cstm_CostOfSales1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	cstm_ProfitAndLossStatementLocationAxis=cstm_OtherGainsAndLossesNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

CURRENCY GAINS / (LOSSES) - Currency Gains and Losses Included in Income from Operations (Details) € in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022 EUR (€)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 EUR (€)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 EUR (€)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 EUR (€)	Jun. 30, 2021 USD ($)
Analysis of income and expense [line items]
Total	€ (7)	$ (7)	€ 0	$ 0	€ (7)	$ (7)	€ 7	$ 7
Realized exchange losses on foreign currency derivatives - net	(2)		(2)		(1)		(5)
Unrealized (losses) / gains on foreign currency derivatives - net	(6)		3		(7)		11
Exchange gains / (losses) from the remeasurement of monetary assets and liabilities - net	1		(1)		1		1
Included in Revenue
Analysis of income and expense [line items]
Total	(1)		0		(2)		(1)
Included in Cost of sales
Analysis of income and expense [line items]
Total	2		0		2		0
Included in Other gains and losses - net
Analysis of income and expense [line items]
Total	€ (8)		€ 0		€ (7)		€ 8