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Investments Accounted for Under Equity Method - Summary of Amounts Included in Financial Statements in Accordance with Group Accounting Principles (Parenthetical) (Detail) € in Millions	6 Months Ended
	Jun. 30, 2018 EUR (€)
Disclosure of investments accounted for using equity method [line items]
Gain related shareholders loan facilities modification	€ 12
Share of losses of joint-ventures in excess of initial investment	28
Group Companies and Constellium UACJ ABS LLC [member]
Disclosure of investments accounted for using equity method [line items]
Loans advanced	104
Share of losses of joint-ventures in excess of initial investment	€ 28

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- Definition

Cumulative share of profit (loss) of joint ventures accounted for using equity method.

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- Definition

Disclosure Of Investments Accounted For Using Equity Method [Line Items]

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No definition available.

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- Definition

Gain on shareholders loan facilities modification.

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No definition available.

+ Details

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- Definition

Loans to joint ventures.

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No definition available.

+ Details

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- Details

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