XML 135 R98.htm IDEA: XBRL DOCUMENT v3.8.0.1

Cash and Cash Equivalents - Additional Information (Detail) - EUR (€) € in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of cash and cash equivalents [line Items]
Cash in bank and on hand	€ 269	€ 347
Subsidiaries in capital control restrictions countries [member]
Disclosure of cash and cash equivalents [line Items]
Cash in bank and on hand	€ 12	€ 7

X

- Definition

Disclosure of cash and cash equivalents.

+ References

No definition available.

+ Details

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

X

- Definition

The amount of cash on hand and demand deposits. [Refer: Cash on hand]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2017-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_45&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_Cash
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=cstm_SubsidiariesInCapitalControlRestrictionsCountriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: