Related party transactions - Post-employment benefits (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Total for all subsidiaries | ||
| Disclosure of transactions between related parties [line items] | ||
| Post-employment benefit plan assets under management of subsidiary | $ 3,800 | $ 3,400 |
| Related party management fees | 15 | 14 |
| Retirement benefit plan deposit assets placed at related party | 400 | 400 |
| Retirement benefit plan interest income earned from related party | 5 | 2 |
| Other related parties | HSBC Bank (UK) Pension Scheme | ||
| Disclosure of transactions between related parties [line items] | ||
| Notional amount with related party | 6,600 | 6,400 |
| Derivative assets with related party | 400 | 400 |
| Cash collateral received with related party | $ 300 | $ 400 |