Provisions for employee benefits (Details 3) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Other comprehensive income [Member]
Remeasurements
Actuarial (gains)/losses due to changes in demographic assumptions	€ (14)	€ (4)
Actuarial (gains)/losses due to changes in financial assumptions	66	40
Experience (gains) losses	(5)	(10)
Return on plan assets	(12)	(42)
Gain (loss) on remeasurement, net defined benefit liability (asset)	35	(16)
TFR [Member]
Remeasurements
Actuarial (gains)/losses due to changes in demographic assumptions		(2)
Actuarial (gains)/losses due to changes in financial assumptions	(5)	11
Experience (gains) losses	(1)	10
Gain (loss) on remeasurement, net defined benefit liability (asset)	(6)	19
Foreign defined benefit plans [Member]
Remeasurements
Actuarial (gains)/losses due to changes in demographic assumptions	(14)	(2)
Actuarial (gains)/losses due to changes in financial assumptions	71	30
Experience (gains) losses	(3)	(6)
Return on plan assets	(12)	(42)
Gain (loss) on remeasurement, net defined benefit liability (asset)	42	(20)
FISDE and other foreign medical plans [Member]
Remeasurements
Actuarial (gains)/losses due to changes in demographic assumptions		(1)
Actuarial (gains)/losses due to changes in financial assumptions		(2)
Experience (gains) losses	(1)	(14)
Gain (loss) on remeasurement, net defined benefit liability (asset)	€ (1)	(17)
Other benefit plans [Member]
Remeasurements
Actuarial (gains)/losses due to changes in demographic assumptions		1
Actuarial (gains)/losses due to changes in financial assumptions		1
Gain (loss) on remeasurement, net defined benefit liability (asset)		€ 2

The amount of gain/loss from experience on defined benefit plan.

No definition available.

Name:	E_GainLossFromExperienceOnDefinedBenefitPlan
Namespace Prefix:	E_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_ii&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ActuarialGainsLossesArisingFromChangesInDemographicAssumptionsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_iii&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ActuarialGainsLossesArisingFromChangesInFinancialAssumptionsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from the remeasurement of that net defined benefit liability (asset). [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_GainLossOnRemeasurementOfNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from the return on plan assets. The return on plans assets is interest, dividends and other revenue derived from the plan assets, together with realised and unrealised gains or losses on the plan assets, less any costs of managing plan assets and less any tax payable by the plan itself, other than tax included in the actuarial assumptions used to measure the present value of the defined benefit obligation. [Refer: Plan assets [member]; Net defined benefit liability (asset); Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_i&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ReturnOnPlanAssetsNetDefinedBenefitLiabilityAsset
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	E_IncomeStatementAxis=us-gaap_OtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=E_TFRMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=ifrs-full_ForeignDefinedBenefitPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=E_SupplementaryMedicalReserveForEniManagersFISDEAndOtherForeignMedicalPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=E_OtherForeignLongTermBenefitPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: