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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	12 Months Ended
	Dec. 31, 2017 EUR (€)
Disclosure of investments accounted for using equity method [line items]
Share of losses of joint-ventures in excess of initial investment	€ 14
Group Companies and Constellium UACJ ABS LLC [member]
Disclosure of investments accounted for using equity method [line items]
Loans advanced	97
Share of losses of joint-ventures in excess of initial investment	€ 14

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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

Loans to joint ventures.

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No definition available.

+ Details

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- Details

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