Segment Information - Summary of Information About Geographical Areas (Detail) - EUR (€) € in Millions	Dec. 31, 2019	Dec. 31, 2018
Disclosure of geographical areas [line items]
Non-current assets	€ 26,548	€ 25,357
Republic of Ireland [member]
Disclosure of geographical areas [line items]
Non-current assets	506	495
United Kingdom [member]
Disclosure of geographical areas [line items]
Non-current assets	2,772	2,461
United States [member]
Disclosure of geographical areas [line items]
Non-current assets	14,259	12,925
Other [member]
Disclosure of geographical areas [line items]
Non-current assets	€ 9,011	€ 9,476

The amount of non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets and rights arising under insurance contracts. [Refer: Deferred tax assets; Financial instruments, class [member]; Non-current assets; Types of insurance contracts [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 33
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_33_b&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_NoncurrentAssetsOtherThanFinancialInstrumentsDeferredTaxAssetsPostemploymentBenefitAssetsAndRightsArisingUnderInsuranceContracts
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant