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SUBSEQUENT EVENTS (Details) € in Millions	Jul. 15, 2020 EUR (€) credit_facility	Jun. 30, 2020 EUR (€)	Dec. 31, 2019 EUR (€)
Disclosure of non-adjusting events after reporting period [line items]
Borrowings		€ 2,536	€ 2,361
Entering Into New Credit Facilities | Constellium Singen GmbH and Constellium Singen Rolled Products | Guaranteed Credit Facilities | German State
Disclosure of non-adjusting events after reporting period [line items]
Number of credit facilities | credit_facility	2
Borrowings	€ 50
Percentage of principal outstanding amount guaranteed	80.00%

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- Definition

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_55&doctype=Standard
-URIDate 2019-03-27

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