Fair Value Disclosures on Financial Instruments - Transfers (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
AFS \| Marketable equity investments
Transfers Between Levels 1 and 2
Transfers of available-for-sale equity investments from Level 2 to Level 1	€ 91	€ 5

The amount of transfers out of Level 2 and into Level 1 of the fair value hierarchy of assets held at the end of the reporting period. [Refer: Level 1 of fair value hierarchy [member]; Level 2 of fair value hierarchy [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_c&doctype=Standard
-URIDate 2020-01-01

Name:	ifrs-full_TransfersOutOfLevel2IntoLevel1OfFairValueHierarchyAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration