FINANCIAL INSTRUMENTS - Schedule of derivatives instruments presented at fair value in the Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	$ 21	$ 2
Fair value of derivatives instruments - current assets	46	24
Fair value of derivatives instruments - assets	67	26
Fair value of derivatives instruments - noncurrent liabilities	3	21
Fair value of derivatives instruments - current liabilities	32	33
Fair value of derivatives instruments - liabilities	35	54
Currency commercial derivatives \| Derivatives that qualify for hedge accounting
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	12	0
Fair value of derivatives instruments - current assets	8	0
Fair value of derivatives instruments - assets	20	0
Fair value of derivatives instruments - noncurrent liabilities	0	13
Fair value of derivatives instruments - current liabilities	0	9
Fair value of derivatives instruments - liabilities	0	22
Currency commercial derivatives \| Derivatives that do not qualify for hedge accounting
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	5	0
Fair value of derivatives instruments - current assets	18	5
Fair value of derivatives instruments - assets	23	5
Fair value of derivatives instruments - noncurrent liabilities	0	7
Fair value of derivatives instruments - current liabilities	5	17
Fair value of derivatives instruments - liabilities	5	24
Currency net debt derivatives \| Derivatives that do not qualify for hedge accounting
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	0	0
Fair value of derivatives instruments - current assets	0	1
Fair value of derivatives instruments - assets	0	1
Fair value of derivatives instruments - noncurrent liabilities	0	0
Fair value of derivatives instruments - current liabilities	2	0
Fair value of derivatives instruments - liabilities	2	0
Energy derivatives \| Derivatives that do not qualify for hedge accounting
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	2	1
Fair value of derivatives instruments - current assets	1	0
Fair value of derivatives instruments - assets	3	1
Fair value of derivatives instruments - noncurrent liabilities	0	0
Fair value of derivatives instruments - current liabilities	2	2
Fair value of derivatives instruments - liabilities	2	2
Metal derivatives \| Derivatives that do not qualify for hedge accounting
Derivatives, Fair Value [Line Items]
Fair value of derivatives instruments - noncurrent assets	2	1
Fair value of derivatives instruments - current assets	19	18
Fair value of derivatives instruments - assets	21	19
Fair value of derivatives instruments - noncurrent liabilities	3	1
Fair value of derivatives instruments - current liabilities	23	5
Fair value of derivatives instruments - liabilities	$ 26	$ 6

CONSTELLIUM SE 10-Q