Pension and other post-employment benefits - Summary of information on plan assets and defined benefit obligation per country (Detail) - EUR (€) € in Millions	Dec. 31, 2025	Dec. 31, 2024
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	€ 2,497	€ 2,636
Defined benefit obligation	2,110	2,219
Funded Status	387	416
- Other assets	528	568
- Other liabilities	(141)	(152)
Netherlands
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	302	325
Defined benefit obligation	381	415
Funded Status	(79)	(90)
USA
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	226	250
Defined benefit obligation	224	235
Funded Status	1	15
United Kingdom
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	1,129	1,206
Defined benefit obligation	706	751
Funded Status	423	455
Belgium
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	514	513
Defined benefit obligation	441	450
Funded Status	72	63
Other countries
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	327	341
Defined benefit obligation	358	368
Funded Status	€ (31)	€ (26)

The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2025-01-01
-Paragraph 57
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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.

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No definition available.

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- Definition

The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

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- Definition

The amount of 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
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-IssueDate 2025-01-01
-Paragraph 55
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-URIDate 2025-03-27

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- Definition

The amount of deficit in a defined benefit plan. [Refer: Defined benefit plans [domain]]

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The fair value of any plan assets, less the present value of the defined benefit obligation. [Refer: Plan assets [member]]

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