Taxes - Schedule of tax liabilities (Details) € in Thousands	12 Months Ended
Dec. 31, 2018 EUR (€) subsidiary	Dec. 31, 2017 EUR (€) subsidiary	Dec. 31, 2016 EUR (€)
Taxes
Current tax payable	€ 1,175	€ 865	€ 1,022
Total tax liabilities	€ 1,175	€ 865	€ 1,022
Number of subsidiaries operating on a cost plus basis \| subsidiary	5	1

The amount of current tax for current and prior periods to the extent unpaid. Current tax is the amount of income taxes payable (recoverable) in respect of the taxable profit (tax loss) for a period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 54
-Subparagraph n
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_54_n&doctype=Standard
-URIDate 2018-03-16

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant