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The amount of acquisition-related costs recognised as an expense for transactions that are recognised separately from the acquisition of assets and the assumption of liabilities in business combinations. [Refer: Business combinations [member]]

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The fair value, at acquisition date, of cash transferred as consideration in a business combination. [Refer: Business combinations [member]]

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The amount recognised as of the business combination's acquisition date for goodwill. [Refer: Goodwill; Business combinations [member]]

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

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The profit (loss) of the combined entity as though the acquisition date for all business combinations that occurred during the year had been as of the beginning of the annual reporting period. [Refer: Business combinations [member]; Profit (loss)]

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ACQUISITION OF CONSTELLIUM-BOWLING GREEN - Narrative (Details) - EUR (€) € in Millions		12 Months Ended
	Jan. 09, 2019	Dec. 31, 2019	Dec. 31, 2020	Jan. 10, 2019
Disclosure of detailed information about business combination [line items]
Preexisting trade receivables with acquiree		€ 393	€ 341
Constellium-UACJ ABS LLC
Disclosure of detailed information about business combination [line items]
Percentage of voting equity interest acquired				49.00%
Consideration transferred				€ 87
Fair value of previously held interest				69
Preexisting trade receivables with acquiree				38
Goodwill				€ 24
Acquisition-related costs recognized as expense in other gains / (losses)		1
Combined revenue		333
Combined net loss		€ 48
Constellium-UACJ ABS LLC
Disclosure of detailed information about business combination [line items]
Proportion of ownership interest in joint venture	51.00%