Provisions for employee benefits - Costs of defined benefit plans recognized in other comprehensive income (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure Of Benefit Plans [Line Items]
Actuarial (gains)/losses due to changes in demographic assumptions	€ 2	€ 9
Actuarial (gains)/losses due to changes in financial assumptions	14	(213)
Experience (gains) losses	14	27
Return on plan assets		117
Change in asset ceiling	1
Remeasurements	31	(60)	€ (119)
Italian defined benefit plans
Disclosure Of Benefit Plans [Line Items]
Actuarial (gains)/losses due to changes in demographic assumptions	1
Actuarial (gains)/losses due to changes in financial assumptions	4	(34)
Experience (gains) losses		8
Remeasurements	5	(26)
Foreign defined benefit plan
Disclosure Of Benefit Plans [Line Items]
Actuarial (gains)/losses due to changes in demographic assumptions	1	9
Actuarial (gains)/losses due to changes in financial assumptions	8	(144)
Experience (gains) losses	15	17
Return on plan assets		117
Change in asset ceiling	1
Remeasurements	25	(1)
FISDE and other foreign medical plans
Disclosure Of Benefit Plans [Line Items]
Actuarial (gains)/losses due to changes in financial assumptions	2	(35)
Experience (gains) losses	(1)	2
Remeasurements	€ 1	€ (33)

No definition available.

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- Definition

The amount of other comprehensive income, before tax, 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: Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions]

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- Definition

The amount of other comprehensive income, before tax, 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: Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions]

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The amount of other comprehensive income, before tax, resulting from actuarial gains (losses) arising from experience adjustments that result in remeasurements of the net defined benefit liability (asset). Experience adjustments deal with the effects of differences between the previous actuarial assumptions and what has actually occurred. [Refer: Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from actuarial gains (losses) arising from experience adjustments]

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- Definition

The amount of other comprehensive income, before tax, resulting from the gain (loss) on changes in the effect of limiting a net defined benefit asset to the asset ceiling, excluding amounts included in interest income or expense. [Refer: Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from gain (loss) on changes in effect of limiting net defined benefit asset to asset ceiling excluding interest income or expense]

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- Definition

The amount of other comprehensive income, before tax, related to gains (losses) on remeasurements of defined benefit plans, which comprise actuarial gains and losses; the return on plan assets, excluding amounts included in net interest on the net defined benefit liability (asset); and any change in the effect of the asset ceiling, excluding amounts included in net interest on the net defined benefit liability (asset). [Refer: Other comprehensive income; Defined benefit plans [member]; Plan assets [member]; Net defined benefit liability (asset)] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from gain (loss) on remeasurement in other comprehensive income]

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The amount of other comprehensive income, before tax, resulting from the return on plan assets, excluding amounts included in interest expense (income) arising from defined benefit plans. The return on plan 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: Other comprehensive income; Defined benefit plans [member]; Plan assets [member]; Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from return on plan assets excluding interest income or expense]

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