Property,Plant and Equipment - Schedule of Future Purchase Commitments for Property, Plant and Equipment (Detail) - EUR (€) € in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [Abstract]
Contracted for but not provided in the financial statements	€ 346	€ 309
Authorised by the Directors but not contracted for	€ 491	€ 467

The amount of contractual commitments for the acquisition of property, plant and equipment. [Refer: Property, plant and equipment]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 16
-IssueDate 2016-01-13
-Paragraph 74
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=16&date=2016-03-30&anchor=para_74_c&doctype=Standard
-URIDate 2016-03-31

Name:	ifrs-full_ContractualCommitmentsForAcquisitionOfPropertyPlantAndEquipment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant