Provisions for employee benefits - Effects of a possible change in the main actuarial assumptions (Details) - EUR (€) € in Millions	Dec. 31, 2020	Dec. 31, 2019
Statement
Percentage of reasonably possible increase in actuarial assumption	0.50%	0.50%
Percentage of reasonably possible decrease in actuarial assumption	0.50%	0.50%
Other benefit plans \| Actuarial assumption of discount rates
Statement
Increase (decrease) in other benefit obligation due to reasonably possible increase in actuarial assumption	€ (3)	€ (4)
Increase (decrease) in other benefit obligation due to reasonably possible decrease in actuarial assumption	1	1
Other benefit plans \| Actuarial assumption of expected rates of inflation
Statement
Increase (decrease) in other benefit obligation due to reasonably possible increase in actuarial assumption	1	1
Italian defined benefit plans \| Actuarial assumption of discount rates
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	(10)	(12)
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption	6	13
Italian defined benefit plans \| Actuarial assumption of expected rates of inflation
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	7	8
Foreign defined benefit plan \| Actuarial assumption of discount rates
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	(84)	(67)
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption	92	77
Foreign defined benefit plan \| Actuarial assumption of expected rates of inflation
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	47	31
Foreign defined benefit plan \| Actuarial assumption of expected rates of salary increases
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	25	18
Foreign defined benefit plan \| Actuarial assumption of expected rates of pension increases
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	67	34
FISDE and other foreign medical plans \| Actuarial assumption of discount rates
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	(10)	(9)
Increase (decrease) in defined benefit obligation due to reasonably possible decrease in actuarial assumption	7	10
FISDE and other foreign medical plans \| Actuarial assumption of medical cost trend rates
Statement
Increase (decrease) in defined benefit obligation due to reasonably possible increase in actuarial assumption	€ 11	€ 10

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- Definition

The increase (decrease) in a other benefit obligation that would have been caused by a decrease in a significant actuarial assumption that was reasonably possible at the end of the reporting period.

+ References

No definition available.

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- Definition

The increase (decrease) in a other benefit obligation that would have been caused by an increase in a significant actuarial assumption that was reasonably possible at the end of the reporting period.

+ References

No definition available.

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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by a decrease in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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- Definition

The increase (decrease) in a defined benefit obligation that would have been caused by an increase in a significant actuarial assumption that was reasonably possible at the end of the reporting period. [Refer: Actuarial assumptions [member]]

+ References

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- Definition

The reasonably possible percentage of the decrease in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

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The reasonably possible percentage of the increase in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]]

+ References

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