Property, plant and equipment (Details 4) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment
Costs for exploratory wells suspended at the beginning of the period	€ 1,684	€ 1,737	€ 1,568
Increases for which is ongoing the determination of proved reserves	451	282	550
Amounts previously capitalized and expensed in the period	(217)	(109)	(501)
Reclassification to successful exploratory wells following the estimation of proved reserves	(278)	(276)	(30)
Disposals	(199)		(4)
Currency translation differences	(178)	50	154
Costs for exploratory wells suspended at the end of the period	€ 1,263	€ 1,684	€ 1,737

The amount of costs for exploratory well that is pending the determination of proved reserves.

No definition available.

Name:	E_CostsForExploratoryWellsSuspended
Namespace Prefix:	E_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Additions to costs for exploratory well that were added during the reporting period pending the determination of proved reserves.

No definition available.

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

Amount of costs for exploratory well for which proved reserves were not found at the exploratory well.

No definition available.

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

Amount of increase (decrease) in exchange differences for exploratory wells.

No definition available.

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

Disposal of exploratory well during the reporting period.

No definition available.

Name:	E_CostsForExploratoryWellsSuspendedsales
Namespace Prefix:	E_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

No definition available.

Name:	E_DisclosureOfPropertyPlantAndEquipmentExplanatoryAbstract
Namespace Prefix:	E_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Reclassified costs to productive wells on determination of proved reserves.

No definition available.

Name:	E_ReclassificationToProductiveWellsOnDeterminationOfProvedReserves
Namespace Prefix:	E_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration