Financial Risk Management and Financial Instruments - Summary of Changes in Contingent Options Liability (Details) - Contingent Options Liability - EUR (€) € in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Disclosure Of Financial Instruments [Line Items] | |||
| At January 1 | € 3 | € 100 | € 82 |
| (Gain)/loss recognized in profit or loss | € (3) | (97) | 18 |
| At December 31 | € 3 | € 100 | |