Financial Risk Management and Financial Instruments - Summary of Changes in Long Term Investments (Details) - EUR (€) € in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Disclosure Of Financial Instruments [Abstract] | ||
| At January 1 | € 910 | |
| Equity issued in exchange for long term investment | € 910 | |
| Changes in fair value recorded in other comprehensive loss | 720 | |
| Purchase of investment | 16 | |
| At December 31 | € 1,646 | € 910 |