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Finance Costs-Net - Summary of Finance Costs - Net (Parenthetical) (Detail) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Analysis of income and expense [line items]
Other finance expense	€ 3	€ 6	€ 13	€ 8
Capitalisation rate			6.00%	7.00%
Constellium N.V. Senior Notes [member]
Analysis of income and expense [line items]
Interest expense on debt instrument			€ 56	€ 69
Muscle Shoals' Senior Notes [member]
Analysis of income and expense [line items]
Interest expense on debt instrument				7
Revolving Credit Facility 1 [member]
Analysis of income and expense [line items]
Interest expense on debt instrument				€ 3
Pan US ABL Facility [member]
Analysis of income and expense [line items]
Interest expense on debt instrument			2
Constellium UACJ loan modification [member]
Analysis of income and expense [line items]
Other finance expense			€ 6

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- Definition

Analysis of income and expense.

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The amount of interest expense on debt instruments issued. [Refer: Interest expense; Debt instruments issued]

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The amount of finance income or cost that the entity does not separately disclose in the same statement or note. [Refer: Finance income (cost)]

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