v3.26.1
Expected credit loss measurement - Credit loss expense / (release) (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) $ 191 $ 263
Global Wealth Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 7 9
Personal & Corporate Banking    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 147 167
Asset Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Investment Bank    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 110 83
Non-core and Legacy    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) (74) 6
Group Items    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 1 (1)
Stages 1 and 2    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 74 17
Stages 1 and 2 | Global Wealth Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) (9) (10)
Stages 1 and 2 | Personal & Corporate Banking    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 24 14
Stages 1 and 2 | Asset Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Stages 1 and 2 | Investment Bank    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 59 14
Stages 1 and 2 | Non-core and Legacy    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Stages 1 and 2 | Group Items    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 1 (1)
Lifetime expected credit losses | Stage 3    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 189 239
Lifetime expected credit losses | Stage 3 | Global Wealth Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 16 19
Lifetime expected credit losses | Stage 3 | Personal & Corporate Banking    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 122 152
Lifetime expected credit losses | Stage 3 | Asset Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Lifetime expected credit losses | Stage 3 | Investment Bank    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 51 69
Lifetime expected credit losses | Stage 3 | Non-core and Legacy    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 (1)
Lifetime expected credit losses | Stage 3 | Group Items    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Lifetime expected credit losses | Purchased    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) (73) 7
Lifetime expected credit losses | Purchased | Global Wealth Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 (1)
Lifetime expected credit losses | Purchased | Personal & Corporate Banking    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 1 1
Lifetime expected credit losses | Purchased | Asset Management    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Lifetime expected credit losses | Purchased | Investment Bank    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) 0 0
Lifetime expected credit losses | Purchased | Non-core and Legacy    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) (74) 6
Lifetime expected credit losses | Purchased | Group Items    
Disclosure Of Provision Matrix [Line Items]    
Credit loss expense / (release) $ 0 $ 0