XML 102 R92.htm IDEA: XBRL DOCUMENT
v3.21.2

NON-CASH INVESTING AND FINANCING TRANSACTIONS (Details) - EUR (€) € in Millions | 6 Months Ended
--- | ---
Jun. 30, 2021 | Jun. 30, 2020
Disclosure of cash flow statement [Abstract] |  |
Property, plant and equipment acquired by finance lease | € 8 | € 25
Fair value of vested PSUs and RSUs | € 15 | € 0

X
- Definition Additions through noncash finance lease, property, plant and equipment. + References No definition available. + Details
Name: | cstm_AdditionsThroughNoncashFinanceLeasePropertyPlantAndEquipment
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Disclosure of cash flow statement + References No definition available. + Details
Name: | cstm_DisclosureofcashflowstatementAbstract
Namespace Prefix: | cstm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of performance stock units and restricted stock units vested. + References No definition available. + Details
Name: | cstm_FairValueOfPerformanceStockUnitsAndRestrictedStockUnitsVested
Namespace Prefix: | cstm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration