Employees - Summary of Movements in Liabilities (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	€ 2,401	€ 2,569
Gross service cost	(178)	(128)
Special termination benefits	5	14	€ 11
Past service costs including losses/(gains) on curtailments	32	3
Actuarial gains/(losses) arising from changes in demographic assumptions	26	98
Actuarial gains/(losses) arising from changes in financial assumptions	903	(552)
Actuarial gain/(loss) arising from experience adjustments	28	(416)
Benefit payments	0	0
Other	20	0
Currency retranslation	72	186
Net defined benefit liability (asset)	2,970	2,401	2,569
Increase (decrease) resulting from reclassification to defined benefit		0
Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(17,522)	(16,564)
Gross service cost	(178)	(128)
Special termination benefits	(5)	(14)
Past service costs including losses/(gains) on curtailments	32	3
Settlements	5	3
Interest income	(783)	(749)
Actuarial gains/(losses) arising from changes in demographic assumptions	26	98
Actuarial gains/(losses) arising from changes in financial assumptions	903	(552)
Actuarial gain/(loss) arising from experience adjustments	28	(416)
Benefit payments	1,208	1,122
Other	33	(371)
Currency retranslation	(351)	46
Net defined benefit liability (asset)	(16,604)	(17,522)	(16,564)
Increase (decrease) resulting from reclassification to defined benefit		368
UK
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	1,429	1,866
Gross service cost	(51)	(42)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	27	0
Actuarial gains/(losses) arising from changes in demographic assumptions	3	104
Actuarial gains/(losses) arising from changes in financial assumptions	675	(243)
Actuarial gain/(loss) arising from experience adjustments	(14)	(220)
Benefit payments	0	0
Other	0	0
Currency retranslation	58	44
Net defined benefit liability (asset)	1,350	1,429	1,866
UK \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(7,250)	(6,838)
Gross service cost	(51)	(42)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	27	0
Settlements	0	0
Interest income	(337)	(335)
Actuarial gains/(losses) arising from changes in demographic assumptions	3	104
Actuarial gains/(losses) arising from changes in financial assumptions	675	(243)
Actuarial gain/(loss) arising from experience adjustments	(14)	(220)
Benefit payments	492	459
Other	0	0
Currency retranslation	(327)	(135)
Net defined benefit liability (asset)	(6,782)	(7,250)	(6,838)
The Netherlands
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	1,483	1,609
Gross service cost	(4)	(5)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Actuarial gains/(losses) arising from changes in demographic assumptions	13	0
Actuarial gains/(losses) arising from changes in financial assumptions	160	(236)
Actuarial gain/(loss) arising from experience adjustments	154	(99)
Benefit payments	0	0
Other	0	0
Currency retranslation	0	0
Net defined benefit liability (asset)	1,942	1,483	1,609
The Netherlands \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(4,031)	(3,734)
Gross service cost	(4)	(5)
Special termination benefits	0	0
Past service costs including losses/(gains) on curtailments	0	0
Settlements	0	0
Interest income	(126)	(135)
Actuarial gains/(losses) arising from changes in demographic assumptions	13	0
Actuarial gains/(losses) arising from changes in financial assumptions	160	(236)
Actuarial gain/(loss) arising from experience adjustments	154	(99)
Benefit payments	181	178
Other	0	0
Currency retranslation	0	0
Net defined benefit liability (asset)	(3,653)	(4,031)	(3,734)
Rest of world
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(511)	(906)
Gross service cost	(123)	(81)
Special termination benefits	5	14
Past service costs including losses/(gains) on curtailments	5	3
Actuarial gains/(losses) arising from changes in demographic assumptions	10	(6)
Actuarial gains/(losses) arising from changes in financial assumptions	68	(73)
Actuarial gain/(loss) arising from experience adjustments	(112)	(97)
Benefit payments	0	0
Other	20	0
Currency retranslation	14	142
Net defined benefit liability (asset)	(322)	(511)	(906)
Rest of world \| Present value of defined benefit obligation
Disclosure of defined benefit plans [line items]
Net defined benefit liability (asset)	(6,241)	(5,992)
Gross service cost	(123)	(81)
Special termination benefits	(5)	(14)
Past service costs including losses/(gains) on curtailments	5	3
Settlements	5	3
Interest income	(320)	(279)
Actuarial gains/(losses) arising from changes in demographic assumptions	10	(6)
Actuarial gains/(losses) arising from changes in financial assumptions	68	(73)
Actuarial gain/(loss) arising from experience adjustments	(112)	(97)
Benefit payments	535	485
Other	33	(371)
Currency retranslation	(24)	181
Net defined benefit liability (asset)	€ (6,169)	€ (6,241)	€ (5,992)

The decrease (increase) in a net defined benefit liability (asset) 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: Net defined benefit liability (asset)]

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- Definition

The decrease (increase) in a net defined benefit liability (asset) 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: Net defined benefit liability (asset)]

+ References

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The decrease (increase) in a net defined benefit liability (asset) 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: Net defined benefit liability (asset)]

+ References

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

The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)]

+ References

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

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The decrease (increase) in the net defined benefit liability (asset) resulting from settlements. Settlements are transactions that eliminate all further legal or constructive obligations for part or all of the benefits provided under a defined benefit plan, other than a payment of benefits to, or on behalf of, employees that is set out in the terms of the plan and included in the actuarial assumptions. [Refer: Net defined benefit liability (asset); Defined benefit plans [domain]; Actuarial assumptions [domain]]

+ References

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-Name IAS
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

+ References

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-Name IAS
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- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [domain]]

+ References

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-Name IAS
-Number 19
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The increase (decrease) in the net defined benefit liability (asset) resulting from past service cost. Past service cost is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting from a plan amendment (the introduction or withdrawal of, or changes to, a defined benefit plan) or a curtailment (a significant reduction by the entity in the number of employees covered by a plan). [Refer: Net defined benefit liability (asset); Defined benefit plans [domain]]

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The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2024-01-01
-Paragraph 141
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- Definition

The amount of expense in relation to termination benefits. Termination benefits are employee benefits provided in exchange for the termination of an employee's employment as a result of either: (a) an entity's decision to terminate an employee's employment before the normal retirement date; or (b) an employee's decision to accept an offer of benefits in exchange for the termination of employment. [Refer: Employee benefits expense]

+ References

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- Definition

Decrease (Increase) In Net Defined Benefit Liability (Asset) Resulting From Reclassification

+ References

No definition available.

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