XML 562 R133.htm IDEA: XBRL DOCUMENT
v3.20.4

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Amounts Recognized in the Consolidated Statement of Financial Position (Details) - EUR (€) € in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Disclosure of net defined benefit liability (asset) [line items] |  |
Present value of funded obligation | € 772 | € 768
Fair value of plan assets | (458) | (445)
Deficit of funded plans | 314 | 323
Present value of unfunded obligation | 350 | 347
Net liability arising from defined benefit obligation | 664 | 670
Pension Benefits |  |
Disclosure of net defined benefit liability (asset) [line items] |  |
Present value of funded obligation | 772 | 768
Fair value of plan assets | (458) | (445)
Deficit of funded plans | 314 | 323
Present value of unfunded obligation | 134 | 127
Net liability arising from defined benefit obligation | 448 | 450
Other Benefits |  |
Disclosure of net defined benefit liability (asset) [line items] |  |
Present value of funded obligation | 0 | 0
Fair value of plan assets | 0 | 0
Deficit of funded plans | 0 | 0
Present value of unfunded obligation | 216 | 220
Net liability arising from defined benefit obligation | € 216 | € 220

X
- Definition Present value of unfunded obligation. + References No definition available. + Details
Name: | cstm_PresentValueOfUnfundedObligation
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2020-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_57_a&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_DefinedBenefitObligationAtPresentValue
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfNetDefinedBenefitLiabilityAssetLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of non-current net defined benefit liability. [Refer: Net defined benefit liability] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_55&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_NoncurrentRecognisedLiabilitiesDefinedBenefitPlan
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2020-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_57_a&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_PlanAssetsAtFairValue
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value of any plan assets, less the present value of the defined benefit obligation. [Refer: Plan assets [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2020-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_57_a&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_SurplusDeficitInPlan
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | ifrs-full_DefinedBenefitPlansAxis=ifrs-full_PensionDefinedBenefitPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_DefinedBenefitPlansAxis=cstm_OtherBenefitPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |