Segment and corporate information - Geographic Information (Details) - EUR (€)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disclosure of geographical areas [line items]
Revenue external customers	€ 4,135,972,000	€ 4,471,021,000	€ 8,189,334,000	€ 9,019,141,000

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

No definition available.

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Data Type:	xbrli:stringItemType
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Period Type:	duration