Related Party Transactions - Additional Information (Details) € in Millions, $ in Millions |
12 Months Ended | |||
|---|---|---|---|---|
|
Dec. 31, 2018
EUR (€)
|
Dec. 31, 2017
EUR (€)
|
Dec. 31, 2016
EUR (€)
|
Apr. 01, 2016
USD ($)
|
|
| Rivers Cross Trust | ||||
| Disclosure Of Transactions Between Related Parties [Line Items] | ||||
| Convertible Notes issued and sold | $ | $ 0.2 | |||
| Soundtrack Your Brand Sweden AB | ||||
| Disclosure Of Transactions Between Related Parties [Line Items] | ||||
| Notional amount | € | € 3 | € 3 | € 2 | |