XML 97 R90.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Borrowings - Summary of Reconciliation of Movement in Net Borrowings Explanatory (Parenthetical) (Detail) € in Millions |  |  | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Nov. 09, 2017 EUR (€) EUR_per_USD | Feb. 16, 2017 EUR (€) EUR_per_USD | Jun. 30, 2017 EUR (€) | Dec. 31, 2017 EUR (€)
Disclosure of detailed information about borrowings [line items] |  |  |  |
Proceeds from the issuance of senior notes |  |  | € 610 | € 1,440
Redemption of senior notes |  |  | € 610 | € 1,559
Constellium N.V. USD Senior Unsecured Notes (Issued November 2017, due 2026) [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Proceeds from the issuance of senior notes | € 830 |  |  |
Exchange rate | EUR_per_USD | 1.1630 |  |  |
Constellium N.V. Senior Unsecured Notes (Issued February 2017, due 2025) [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Proceeds from the issuance of senior notes |  | € 610 |  |
Exchange rate | EUR_per_USD |  | 1.0652 |  |
Senior secured and unsecured notes [member] |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |
Redemption of senior notes | € 949 |  |  |
Exchange rate | EUR_per_USD | 1.1630 |  |  |

X
- Definition The spot exchange rate at the end of the reporting period. Exchange rate is the ratio of exchange for two currencies. Spot exchange rate is the exchange rate for immediate delivery. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_ClosingForeignExchangeRate
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition The cash inflow from the issuing of bonds, notes and debentures. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 7 -IssueDate 2017-01-01 -Paragraph 17 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_17&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_ProceedsFromIssueOfBondsNotesAndDebentures
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash outflow for repayments of bonds, notes and debentures. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 7 -IssueDate 2017-01-01 -Paragraph 17 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_17&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_RepaymentsOfBondsNotesAndDebentures
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=cstm_ConstelliumNvSeniorUnsecuredNotesIssuedNovemberTwoThousandSeventeenDueTwoThousandTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=cstm_ConstelliumNvSeniorUnsecuredNotesIssuedFebruaryTwoThousandSeventeenDueTwoThousandTwentyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=cstm_SeniorSecuredAndUnsecuredNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |