Trade receivables and other recognised as of acquisition date.

No definition available.

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Namespace Prefix:	cstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The fair value, at acquisition date, of the consideration transferred in a business combination. [Refer: Business combinations [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2018-01-01
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount recognised as of the acquisition date for borrowings assumed in a business combination. [Refer: Borrowings; Business combinations [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount recognised as of the acquisition date for cash and cash equivalents acquired in a business combination. [Refer: Cash and cash equivalents; Business combinations [member]]

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

The amount recognised as of the acquisition date for deferred tax assets acquired in a business combination. [Refer: Deferred tax assets; Business combinations [member]]

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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.

No definition available.

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

The amount recognised as of the business combination's acquisition date for goodwill. [Refer: Goodwill; Business combinations [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount recognised as of the acquisition date for net identifiable assets acquired or liabilities assumed in a business combination. [Refer: Business combinations [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Name:	ifrs-full_IdentifiableAssetsAcquiredLiabilitiesAssumed
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount recognised as of the acquisition date for inventory acquired in a business combination. [Refer: Inventories; Business combinations [member]]

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

The amount recognised as of the acquisition date for plant, property and equipment acquired in a business combination. [Refer: Property, plant and equipment; Business combinations [member]]

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

The amount recognised as of the acquisition date for trade and other payables assumed in a business combination. [Refer: Trade and other payables; Business combinations [member]]