Shareholders' Equity - Summary of Remeasurement of Defined Benefit Plans (Detail) - Remeasurement of defined benefit Plans of group companies [member] - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of revaluation reserve [Line Items]
At January 1	€ (1,850)	€ (1,669)	€ (1,820)
Remeasurements of defined benefit plans	(612)	(134)	224
Tax effect	90	(15)	(175)
Net exchange differences	(25)	(32)	102
Total remeasurement of defined benefit plans	€ (2,397)	€ (1,850)	€ (1,669)

A component of equity representing the accumulated remeasurements of defined benefit plans. [Refer: Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 78
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_78_e&doctype=Standard
-URIDate 2019-03-27

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