Property and Equipment - Additional Information (Detail) - EUR (€) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Disclosure Of Property Plant And Equipment [Abstract] | ||
| Accelerated depreciation | € 0 | € 11,000,000 |
| Leasehold improvements not placed into service | € 113,000,000 | € 10,000,000 |