XML 88 R80.htm IDEA: XBRL DOCUMENT
v3.20.2

PROPERTY, PLANT AND EQUIPMENT - Additional Information (Details) - EUR (€) | 6 Months Ended
--- | ---
Jun. 30, 2020 | Jun. 30, 2019
Disclosure of detailed information about property, plant and equipment [abstract] |  |
Expense related to short-term leases, low value asset leases and variable lease still recognized as operating expenses | € 6,000,000 | € 7,000,000
Impairment charges related to cash-generating units | € 0 |
Average percentage of operating level of plants | 50.00% |
Impairment loss recognised in profit or loss, property, plant and equipment | € 5,000,000 |

X
- Definition Average Percentage Of Operating Capacity Of Plants + References No definition available. + Details
Name: | cstm_AveragePercentageOfOperatingCapacityOfPlants
Namespace Prefix: | cstm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expense Relating To Short-term Leases, Leases Of Low-value Assets And Variable Lease Payments For Which Recognition Exemption Has Been Used + References No definition available. + Details
Name: | cstm_ExpenseRelatingToShorttermLeasesLeasesOfLowvalueAssetsAndVariableLeasePaymentsForWhichRecognitionExemptionHasBeenUsed
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | ifrs-full_DisclosureOfPropertyPlantAndEquipmentAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount recognised as a reduction of the carrying amount of an asset or cash-generating unit to its recoverable amount. [Refer: Carrying amount [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2019-01-01 -Paragraph 130 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2019-en-r&anchor=para_130_b&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2019-01-01 -Paragraph 130 -Subparagraph d -Clause ii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2019-en-r&anchor=para_130_d_ii&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_ImpairmentLoss
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of impairment loss recognised in profit or loss for property, plant and equipment. [Refer: Impairment loss recognised in profit or loss; Property, plant and equipment] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 16 -IssueDate 2019-01-01 -Paragraph 73 -Subparagraph e -Clause v -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=16&code=ifrs-tx-2019-en-r&anchor=para_73_e_v&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 98 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_98_a&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration