Operating costs - Summary of sales and marketing expenses (Details) - EUR (€) € in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating costs
Personnel costs	€ (7,558)	€ (2,282)	€ (2,156)
Depreciation	(61)
External outsourcing costs	(15,722)	(1,284)	(42)
Other operating expenses	(1,236)	(580)	(604)
Total sales and marketing expenses	€ (24,577)	€ (4,146)	€ (2,803)

The amount of expense relating to the marketing and selling of goods or services.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 85
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_85&doctype=Standard
-URIDate 2019-03-27

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration