Other information about investments - Principal joint ventures, joint operations and associates (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Var Energi AS
Disclosure of detailed information about investments
Company name	Vår Energi AS
Registered office	Forus (Norway)
Country of operation	Norway
Business segment	Exploration & Production
% ownership interest	69.60%	69.60%
Eni's % of the investment	69.60%	69.60%
Saipem SpA
Disclosure of detailed information about investments
Company name	Saipem SpA
Registered office	San Donato Milanese (MI) (Italy)
Country of operation	Italy
Business segment	Other Activities
% ownership interest	30.54%
Eni's % of the investment	30.99%	30.99%
Union Fenosa Gas SA
Disclosure of detailed information about investments
Company name	Unión Fenosa Gas SA
Registered office	Madrid (Spain)
Country of operation	Spain
Business segment	Gas & Power
% ownership interest	50.00%
Eni's % of the investment	50.00%	50.00%
Cardon IV SA
Disclosure of detailed information about investments
Company name	Cardón IV SA
Registered office	Caracas (Venezuela)
Country of operation	Venezuela
Business segment	Exploration & Production
% ownership interest	50.00%
Eni's % of the investment	50.00%	50.00%
Gas Distribution Company of Thessaloniki Thessaly SA
Disclosure of detailed information about investments
Company name	Gas Distribution Company of Thessaloniki - Thessaly SA
Registered office	Ampelokipi- Menemeni (Greece)
Country of operation	Greece
Business segment	Gas & Power
% ownership interest	49.00%
Eni's % of the investment	49.00%	49.00%
Abu Dhabi Oil Refining Co
Disclosure of detailed information about investments
Company name	Abu Dhabi Oil Refining Co (Takreer)
Registered office	Abu Dhabi (United Arab Emirates)
Country of operation	United Arab Emirates
Business segment	Refining & Marketing
% ownership interest	20.00%
Eni's % of the investment	20.00%
Angola LNG Ltd
Disclosure of detailed information about investments
Company name	Angola LNG Ltd
Registered office	Hamilton (Bermuda)
Country of operation	Angola
Business segment	Exploration & Production
% ownership interest	13.60%
Eni's % of the investment	13.60%	13.60%
Coral FLNG SA
Disclosure of detailed information about investments
Company name	Coral FLNG SA
Registered office	Maputo (Mozambique)
Country of operation	Mozambique
Business segment	Exploration & Production
% ownership interest	25.00%
Eni's % of the investment	25.00%	25.00%
Mozambique Rovuma Venture SpA
Disclosure of detailed information about investments
Company name	Mozambique Rovuma Venture SpA
Registered office	San Donato Milanese (MI) (Italy)
Country of operation	Mozambique
Business segment	Exploration & Production
% ownership interest	35.71%
Eni's % of the investment	35.71%
Raffineria di Milazzo ScpA
Disclosure of detailed information about investments
Company name	Raffineria di Milazzo ScpA
Registered office	Milazzo (ME) (Italy)
Country of operation	Italy
Business segment	Refining & Marketing
% ownership interest	50.00%
Eni's % of the investment	50.00%
GreenStream BV
Disclosure of detailed information about investments
Company name	GreenStream BV
Registered office	Amsterdam (Netherlands)
Country of operation	Libya
Business segment	Gas & Power
% ownership interest	50.00%
Eni's % of the investment	50.00%
Blue Stream Pipeline Co BV
Disclosure of detailed information about investments
Company name	Blue Stream Pipeline Co BV
Registered office	Amsterdam (Netherlands)
Country of operation	Russia
Business segment	Gas & Power
% ownership interest	74.62%
Eni's % of the investment	74.62%

The business segment.

No definition available.

Name:	e_BusinessSegment
Namespace Prefix:	e_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	e_DisclosureOfDetailedInformationAboutInvestmentsLineItems
Namespace Prefix:	e_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The address at which the entity's office is registered.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 138
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_138_a&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_AddressOfRegisteredOfficeOfEntity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The name of an associate. [Refer: Associates [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 17
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_17_b_i&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 16
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_16_b_i&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_i&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_NameOfAssociate
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The name of a joint operation. [Refer: Joint operations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_i&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_NameOfJointOperation
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The name of a joint venture. [Refer: Joint ventures [member]]

+ References

+ Details

Name:	ifrs-full_NameOfJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The principal place of business of an associate. [Refer: Principal place of business; Associates [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 16
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_16_b_ii&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 17
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_17_b_ii&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_iii&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_PrincipalPlaceOfBusinessOfAssociate
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The principal place of business of a joint operation. [Refer: Joint operations [member]; Principal place of business]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_iii&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_PrincipalPlaceOfBusinessOfJointOperation
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The principal place of business of a joint venture. [Refer: Principal place of business; Joint ventures [member]]

+ References

+ Details

Name:	ifrs-full_PrincipalPlaceOfBusinessOfJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of ownership interest in an associate attributable to the entity. [Refer: Associates [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_17_b_iii&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2019-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=27&code=ifrs-tx-2019-en-r&anchor=para_16_b_iii&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_iv&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInAssociate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of ownership interest in a joint operation attributable to the entity. [Refer: Joint operations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph 21
-Subparagraph a
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_21_a_iv&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInJointOperation
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of ownership interest in a joint venture attributable to the entity. [Refer: Joint ventures [member]]

+ References

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of the voting rights in an associate held by the entity. [Refer: Associates [member]]

+ References

+ Details

Name:	ifrs-full_ProportionOfVotingPowerHeldInAssociate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of the voting rights in a joint operation held by the entity. [Refer: Joint operations [member]]

+ References

+ Details

Name:	ifrs-full_ProportionOfVotingRightsHeldInJointOperation
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The proportion of the voting rights in a joint venture held by the entity. [Refer: Joint ventures [member]]

+ References

+ Details

Name:	ifrs-full_ProportionOfVotingRightsHeldInJointVenture
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_JointVenturesAxis=e_VarEnergiASMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointVenturesAxis=e_SaipemSpAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointVenturesAxis=e_UnionFenosaGasSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointVenturesAxis=e_CARDONIVSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointVenturesAxis=e_GasDistributionCompanyOfThessalonikiThessalySAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=e_AbuDhabiOilRefiningCoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=e_AngolaLNGLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=e_CoralFLNGSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointOperationsAxis=e_MozambiqueRovumaVentureSpAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointOperationsAxis=e_RaffMilazzoScpAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointOperationsAxis=e_GreenstreamBvMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_JointOperationsAxis=e_BlueStreamPipelineCoBvMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: