Segment and corporate information - Geographic Information (Details) - EUR (€)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Disclosure of geographical areas [line items]
Revenue external customers	€ 3,975,629,000	€ 4,548,120,000

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.

Name:	ifrs-full_DisclosureOfGeographicalAreasLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration