Post-retirement benefits - Summary of fair value of plan assets (Detail)	Dec. 31, 2024	Dec. 31, 2023
Disclosure of information about defined benefit plans [abstract]
Equities	17.60%	16.60%
– Quoted	11.10%	11.10%
– Private	6.50%	5.50%
Bonds	47.70%	47.40%
– Government fixed income	21.00%	21.60%
– Government inflation-linked	1.60%	1.60%
– Corporate and other publicly quoted	17.50%	16.50%
– Private	7.60%	7.70%
Property	6.90%	8.70%
– Quoted property funds	2.20%	2.50%
– Unquoted property funds	4.70%	6.20%
Qualifying insurance policies	24.30%	24.90%
Cash and other	3.50%	2.40%
Total	100.00%	100.00%

The percentage cash and cash equivalents contribute to the fair value of defined benefit plan assets. [Refer: Cash and cash equivalents; Plan assets, at fair value; Defined benefit plans [domain]] [Contrast: Cash and cash equivalents, amount contributed to fair value of plan assets]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2024-01-01
-Paragraph 142
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_142_a&doctype=Standard
-URIDate 2024-03-27