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FINANCIAL RISK MANAGEMENT - Effect of Foreign Currency Derivatives Impacts and Commercial Transactions Exposures (Details) - EUR (€) € in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |  |
Realized (losses) / gains on foreign currency derivatives - net | € (11) | € 1 | € 11
Unrealized gains / (losses) on foreign currency derivatives - net | (8) | 1 | (3)
Losses reclassified from OCI as a result of hedge accounting discontinuation | 6 | 0 | 0
Derivatives that do not qualify for hedge accounting | At Fair Value through Profit and loss |  |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |  |
Realized (losses) / gains on foreign currency derivatives - net | (4) | 7 | 7
Unrealized gains / (losses) on foreign currency derivatives - net | (9) | 2 | (1)
Derivatives that qualify for hedge accounting | At Fair Value through Profit and loss |  |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |  |
Realized (losses) / gains on foreign currency derivatives - net | (7) | (6) | 4
Unrealized gains / (losses) on foreign currency derivatives - net | 1 | (1) | (2)
Losses reclassified from OCI as result of hedge accounting discontinuation | (6) | 0 | 0
Losses reclassified from OCI as a result of hedge accounting discontinuation | 6 |  |
Derivatives that qualify for hedge accounting | At Fair Value through OCI |  |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |  |
Unrealized gains / (losses) on foreign currency derivatives - net | 20 | (15) | (23)
Gains / (losses) reclassified from cash flow hedge reserve to Consolidated Income Statement | € 6 | € 7 | € (2)

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- Definition Unrealized gains (losses) on foreign currency derivatives - net. + References No definition available. + Details
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