XML 553 R142.htm IDEA: XBRL DOCUMENT v3.22.0.1

COVID-19-RELATED GOVERNMENT ASSISTANCE (Details) € in Millions	12 Months Ended
	Dec. 31, 2020 EUR (€)
COVID-19
Government Assistance [Line Items]
Proceeds from government grants deducted from employee benefit expenses	€ 22

X

- Definition

Government Assistance

+ References

No definition available.

+ Details

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

X

- Definition

The amount of income recognised in relation to government grants. [Refer: Government grants]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 20
-IssueDate 2021-01-01
-Paragraph 39
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=20&code=ifrs-tx-2021-en-r&anchor=para_39_b&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_RevenueFromGovernmentGrants
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	cstm_UnusualOrInfrequentItemOrBoth1Axis=cstm_COVID19PandemicMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: