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BORROWINGS - Currency Concentration of Total Borrowings (Details) - EUR (€) € in Millions | Jun. 30, 2021 | Dec. 31, 2020 | Dec. 31, 2019
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Disclosure of detailed information about borrowings [line items] |  |  |
Total Borrowings | € 2,257 | € 2,391 | € 2,361
U.S. Dollars |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Total Borrowings | 1,182 | 1,602 |
Euro |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Total Borrowings | 1,048 | 757 |
Other currencies |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Total Borrowings | € 27 | € 32 |

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