XML 105 R97.htm IDEA: XBRL DOCUMENT
v3.20.2

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Amounts Recognized in the Consolidated Income Statement (Details) - EUR (€) € in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018
Included in the Unaudited Interim Consolidated Income Statement |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |
Current service cost | € (6) | € (6) | € (14) | € (12) |  |
Past service cost | (2) | 0 | (2) | 0 |  |
Net interest | (3) | (4) | (6) | (8) |  |
Immediate recognition of gains / (losses) arising over the period | (1) | (2) | 0 | (2) |  |
Administration expenses | (1) | 0 | (1) | (1) |  |
Total | (13) | (12) | (23) | (23) |  |
Pension Benefits | Included in the Unaudited Interim Consolidated Income Statement |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |
Current service cost | (5) | (5) | (11) | (9) |  |
Past service cost | 0 | 0 | 0 | 0 |  |
Net interest | (2) | (2) | (3) | (4) |  |
Immediate recognition of gains / (losses) arising over the period | 0 | 0 | 0 | 0 |  |
Administration expenses | (1) | 0 | (1) | (1) |  |
Total | (8) | (7) | (15) | (14) |  |
Other Benefits |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |
Past service cost |  |  | (2) |  | € (3) | € (36)
Other Benefits | Included in the Unaudited Interim Consolidated Income Statement |  |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |  |
Current service cost | (1) | (1) | (3) | (3) |  |
Past service cost | (2) | 0 | (2) | 0 |  |
Net interest | (1) | (2) | (3) | (4) |  |
Immediate recognition of gains / (losses) arising over the period | (1) | (2) | 0 | (2) |  |
Administration expenses | 0 | 0 | 0 | 0 |  |
Total | € (5) | € (5) | € (8) | € (9) |  |

X
- Definition Defined Benefit Plan Net Periodic (Benefit) Cost1 + References No definition available. + Details
Name: | cstm_DefinedBenefitPlanNetPeriodicBenefitCost1
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Immediate recognition actuarial gains (losses) arising from change in assumption recognized in profit (loss). + References No definition available. + Details
Name: | cstm_ImmediateRecognitionActuarialGainsLossesArisingFromChangeInAssumptionRecognizedInProfitLoss
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of expenses that the entity classifies as being administrative. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 26 -IssueDate 2019-01-01 -Paragraph 35 -Subparagraph b -Clause vi -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=26&code=ifrs-tx-2019-en-r&anchor=para_35_b_vi&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 103 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_103&doctype=Standard -URIDate 2019-03-27 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 99 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_99&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_AdministrativeExpense
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 141 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_141_a&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_CurrentServiceCostNetDefinedBenefitLiabilityAsset
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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_DisclosureOfDefinedBenefitPlansLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of income or expense arising from interest. [Refer: Interest expense; Interest income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2019-01-01 -Paragraph 28 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_28_e&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2019-01-01 -Paragraph 23 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_23&doctype=Standard -URIDate 2019-03-27 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_85&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_InterestRevenueExpense
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from past service cost. Past service cost is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting from a plan amendment (the introduction or withdrawal of, or changes to, a defined benefit plan) or a curtailment (a significant reduction by the entity in the number of employees covered by a plan). [Refer: Net defined benefit liability (asset); Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 141 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_141_d&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_PastServiceCostNetDefinedBenefitLiabilityAsset
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ifrs-full_ConsolidatedAndSeparateFinancialStatementsAxis=cstm_IncomeStatementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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: |