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Share of Income / Loss Joint Ventures - Additional Information (Detail) - Constellium-Bowling Green [member] - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2019	Jan. 10, 2019
Disclosure of classes of share capital [line items]
Percentage of voting equity interests acquired		49.00%
Total percentage of voting equity interests acquired		51.00%
Remeasurement profit	€ 5

X

- Definition

Remeasurement of percentage of voting equity interests acquired.

+ References

No definition available.

+ Details

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- Definition

Remeasurement profit.

+ References

No definition available.

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- 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.

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X

- Definition

The percentage of voting equity interests acquired in a business combination. [Refer: Business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2018-01-01
-Paragraph B64
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=3&date=2018-03-01&anchor=para_B64_c&doctype=Appendix&seq=2
-URIDate 2018-03-16

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