XML 105 R95.htm IDEA: XBRL DOCUMENT v3.21.2

SHARE-BASED COMPENSATION - Narrative (Details) € / shares in Units, € in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020 shares	Jun. 30, 2021 EUR (€) shares € / shares	Jun. 30, 2020 EUR (€) shares	Jun. 30, 2018
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		1,149,054
Expense from share-based payment transactions with employees | €		€ 7	€ 8
Antidilutive securities (in shares)	4,880,758		4,878,787
PSUs
Share Based Payment Plans [line items]
Share based compensation, vesting period		3 years
Fair value at grant date (in euros) (in EUR per share) | € / shares		€ 21.84
PSUs | Bottom of range
Share Based Payment Plans [line items]
Percentage of vesting multiplier		0.00%
PSUs | Top of range
Share Based Payment Plans [line items]
Percentage of vesting multiplier		200.00%
PSUs granted in May 2018
Share Based Payment Plans [line items]
Total shareholder return (TSR) percentage achieved				182.90%
PSUs vested in May 2021
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		1,161,718
RSUs
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		534,499
Vesting period on the grant date		3 years
Fair value at grant date (in euros) (in EUR per share) | € / shares		€ 13.9

X

- Definition

Fair value at measurement date other equity instruments granted per share.

+ References

No definition available.

+ Details

Name:	cstm_FairValueAtMeasurementDateOtherEquityInstrumentsGrantedPerShare
Namespace Prefix:	cstm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Instruments With Potential Future Dilutive Effect Not Included In Calculation Of Diluted Earnings Per Share

+ References

No definition available.

+ Details

Name:	cstm_InstrumentsWithPotentialFutureDilutiveEffectNotIncludedInCalculationOfDilutedEarningsPerShare
Namespace Prefix:	cstm_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of sharebased payments vesting multiplier.

+ References

No definition available.

+ Details

Name:	cstm_PercentageOfSharebasedPaymentsVestingMultiplier
Namespace Prefix:	cstm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share based compensation vesting period.

+ References

No definition available.

+ Details

Name:	cstm_ShareBasedCompensationVestingPeriod
Namespace Prefix:	cstm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share based Payment Arrangement Vesting Period

+ References

No definition available.

+ Details

Name:	cstm_ShareBasedPaymentArrangementVestingPeriod
Namespace Prefix:	cstm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Share based payment plans.

+ References

No definition available.

+ Details

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

X

- Definition

Sharebased Compensation stockholders return percentage.

+ References

No definition available.

+ Details

Name:	cstm_SharebasedCompensationStockholdersReturnPercentage
Namespace Prefix:	cstm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of expense from share-based payment transactions with employees.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_ExpenseFromSharebasedPaymentTransactionsWithEmployees
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=cstm_PerformanceShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=cstm_PerformanceShareUnitsGrantedInMayTwoThousandAndEighteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=cstm_PerformanceShareUnitsVestedInMayTwoThousandAndTwentyOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=cstm_RestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: