Income taxes - Reconciliation between statutory tax and effective tax charge (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Profit (loss) before taxation	€ (5,978)	€ 5,746	€ 10,107
Tax rate (IRES) (%)	24.00%	24.00%	24.00%
Statutory corporation tax charge (credit) on profit or loss	€ (1,435)	€ 1,379	€ 2,426
Increase (decrease) resulting from:
- higher tax charges related to subsidiaries outside Italy	1,980	2,934	3,096
- impact pursuant to the write-down of deferred tax assets and recalculation of tax rates	1,785	938	261
- impact pursuant to foreign tax effects of italian entities	108	105	46
- Italian regional income tax (IRAP)	107	25	50
- effect due to the tax regime provided for intercompany dividends	96	65	47
- tax effects related to previous years	(30)	147	(24)
- other adjustments	39	(2)	68
Net tax effect	4,085	4,212	3,544
Income tax expense	2,650	5,591	5,970
Exploration & Production
Increase (decrease) resulting from:
- higher tax charges related to subsidiaries outside Italy	€ 1,777	€ 2,934	€ 3,014

Disclosure of Income Tax Explanatory.

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

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

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

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

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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.

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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.

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Amount of tax effects related to previous years.

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The applicable income tax rate.

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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)]

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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]

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

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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]

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

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