Trade accounts receivable - Development of allowance for doubtful accounts (Details)	3 Months Ended
Mar. 31, 2018 EUR (€)
Development of Allowance For Doubtful Accounts
Allowance for doubtful accounts, beginning of period	€ 474,891,000
Change in valuation allowances as recorded in the consolidated statements of income	€ 357,119,000

The increase (decrease) in allowance account for credit losses of financial assets resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Allowance account for credit losses of financial assets]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_16&doctype=Standard&book=B
-URIDate 2017-03-09

Name:	ifrs-full_IncreaseDecreaseThroughOtherChangesAllowanceAccountForCreditLossesOfFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration