Segment Information - Additional Information (Details)	Dec. 31, 2018 EUR (€) Segment	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 EUR (€)
Disclosure Of Operating Segments [Line Items]
Number of reportable segment \| Segment	2
Property and equipment	€ 197,000,000	€ 73,000,000
Luxembourg
Disclosure Of Operating Segments [Line Items]
Property and equipment	€ 0	€ 0	€ 0

The amount of tangible assets that: (a) are held for use in the production or supply of goods or services, for rental to others, or for administrative purposes; and (b) are expected to be used during more than one period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2017-01-01
-Paragraph 73
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=16&date=2017-03-01&anchor=para_73_e&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_a&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_PropertyPlantAndEquipment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant