Income taxes - Reconciliation between statutory tax and effective tax charge (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Profit (loss) before taxation	€ 5,746	€ 10,107	€ 6,844
Tax rate (IRES) (%)	24.00%	24.00%	24.00%
Statutory corporation tax charge (credit) on profit or loss	€ 1,379	€ 2,426	€ 1,643
Increase (decrease) resulting from:
- higher tax charges related to subsidiaries outside Italy	2,934	3,096	1,882
- impact pursuant to the write-down of deferred tax assets and recalculation of tax rates	938	261	(96)
- tax effects related to previous years	147	(24)	(1)
- impact pursuant to foreign tax effects of italian entities	105	46	54
- effect due to the tax regime provided for intercompany dividends	65	47	1
- Italian regional income tax (IRAP)	25	50	77
- impact pursuant to redetermination of the Italian Windfall Corporate tax as per Law 7/2009			61
- effect due to non-taxable gains/losses on sales of investments		(1)	(177)
- other adjustments	(2)	69	23
Net tax effect	4,212	3,544	1,824
Income tax expense	5,591	5,970	3,467
Exploration & Production
Increase (decrease) resulting from:
- higher tax charges related to subsidiaries outside Italy	€ 2,934	€ 3,014	€ 1,811

Disclosure of Income Tax Explanatory.

No definition available.

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

- Definition

Amount of impact pursuant to foreign tax effects of italian entities.

+ References

No definition available.

+ Details

Name:	e_ImpactPursuantToForeignTaxEffectsOfItalianEntities
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Impact pursuant to the write-down of deferred tax assets and recalculation of tax rates

+ References

No definition available.

+ Details

Name:	e_ImpactPursuantToWriteDownOfDeferredTaxAssetsAndRecalculationOfTaxRates
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Increase Decrease Tax Expense Income At Applicable Tax Rate [Abstract]

+ References

No definition available.

+ Details

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

- Definition

Net tax effects during the period for reconciliation between accounting profit and tax expense (income)

+ References

No definition available.

+ Details

Name:	e_NetTaxEffect
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tax Effect Due To Non-Taxable Gains (Losses) On Sales Of Investments

+ References

No definition available.

+ Details

Name:	e_TaxEffectDueToNonTaxableGainsLossesOnSalesOfInvestments
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to the tax regime provided for intercompany dividends.

+ References

No definition available.

+ Details

Name:	e_TaxEffectDueToTaxRegimeProvidedForInterCompanyDividends
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tax effect from windfall corporate tax

+ References

No definition available.

+ Details

Name:	e_TaxEffectFromWindfallCorporateTax
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to regional income tax.

+ References

No definition available.

+ Details

Name:	e_TaxEffectOfRegionalIncomeTax
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of tax effects related to previous years.

+ References

No definition available.

+ Details

Name:	e_TaxEffectsRelatedToPreviousYears
Namespace Prefix:	e_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The applicable income tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 26
-IssueDate 2019-01-01
-Paragraph 35
-Subparagraph b
-Clause viii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=26&code=ifrs-tx-2019-en-r&anchor=para_35_b_viii&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 23
-Subparagraph h
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_23_h&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 79
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_79&doctype=Standard
-URIDate 2019-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2019-03-27

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 82
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_82_d&doctype=Standard
-URIDate 2019-03-27

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2019-03-27

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2019-01-01
-Paragraph B13
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2019-en-r&anchor=para_B13_g&doctype=Appendix&subtype=B
-URIDate 2019-03-27

+ Details

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

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that the entity does not separately disclose in the same statement or note. [Refer: Accounting profit; Applicable tax rate]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Definition

The profit (loss) before tax expense or income. [Refer: Profit (loss)]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 28
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_28_b&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 8
-IssueDate 2019-01-01
-Paragraph 23
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2019-en-r&anchor=para_23&doctype=Standard
-URIDate 2019-03-27

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 103
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_103&doctype=Standard
-URIDate 2019-03-27

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 102
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_102&doctype=Standard
-URIDate 2019-03-27

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 5
-IssueDate 2019-01-01
-Paragraph 33
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=5&code=ifrs-tx-2019-en-r&anchor=para_33_b_i&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_ProfitLossBeforeTax
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit]

+ References

+ Details

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

- Definition

The product of the accounting profit multiplied by the applicable tax rate(s). [Refer: Accounting profit; Applicable tax rate]

+ References

+ Details

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

- Details

Name:	ifrs-full_SegmentsAxis=e_ExplorationAndProductionSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: