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Other Gains / (Losses) - Net - Summary of Other Gains/(Losses) Net (Detail) - EUR (€) € in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Analysis of other gains losses [line items] |  |  |
Realized gains/(losses) on derivatives |  | € (62) | € (93)
Unrealized gains / (losses) on derivatives at fair value through profit and loss-net | € 57 | 71 | (20)
Unrealized exchange (losses) /gains from the remeasurement of monetary assets and liabilities-net | (4) | 3 | (3)
Gains / (Losses) on pension plan amendments | 20 |  | (5)
Losses on disposal | (3) | (10) | (5)
Wise purchase price adjustment |  | 20 |
Wise acquisition costs |  |  | (5)
Other |  | (1) |
Total other gains / (losses)-net | € 70 | 21 | € (131)
Wise Metals Intermediate Holdings LLC [member] |  |  |
Analysis of other gains losses [line items] |  |  |
Wise purchase price adjustment |  | € 20 |

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