Notes to the statement of financial position - Inventories narrative (Details) - EUR (€) € in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation And Qualifying Accounts Disclosure1 [Line Items]
Expense for damaged, obsolete and lost inventories	€ 2,446	€ 5,865	€ 3,021
Inventory Valuation Reserve
Valuation And Qualifying Accounts Disclosure1 [Line Items]
Impairment allowance on inventories	€ 1,432	€ 4,208	€ 3,399

The amount of expense recognised related to the write-down of inventories to net realisable value. [Refer: Inventories]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 2
-IssueDate 2017-01-01
-Paragraph 36
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=2&date=2017-03-01&anchor=para_36_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 98
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_98_a&doctype=Standard
-URIDate 2017-03-09

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