Intangible assets - Goodwill related to Gas & Power segment (Details) - EUR (€) € in Millions	Dec. 31, 2019	Dec. 31, 2018
Intangible assets
Goodwill	€ 1,265	€ 1,284
Gas & Power
Intangible assets
Goodwill	981	977
Gas & Power \| CGU Domestic Gas Market
Intangible assets
Goodwill	839	835
Gas & Power \| CGU Foreign Gas Market
Intangible assets
Goodwill	€ 142	€ 142

The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2019-01-01
-Paragraph B67
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2019-en-r&anchor=para_B67_d&doctype=Appendix&subtype=B
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2019-01-01
-Paragraph 134
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2019-en-r&anchor=para_134_a&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2019-01-01
-Paragraph 135
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2019-en-r&anchor=para_135_a&doctype=Standard
-URIDate 2019-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 54
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_54_c&doctype=Standard
-URIDate 2019-03-27

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