v3.24.2.u1
Commitments and contingencies - Narrative (Details) - CHF (SFr)
SFr in Millions
Jun. 30, 2024
Dec. 31, 2023
Disclosure of amounts to be recovered or settled after twelve months for classes of assets and liabilities that contain amounts to be recovered or settled both no more and more than twelve months after reporting date [line items]    
Gross lease liabilities SFr 318.0 SFr 385.7
Belgium    
Disclosure of amounts to be recovered or settled after twelve months for classes of assets and liabilities that contain amounts to be recovered or settled both no more and more than twelve months after reporting date [line items]    
Gross lease liabilities 106.4 122.5
United States    
Disclosure of amounts to be recovered or settled after twelve months for classes of assets and liabilities that contain amounts to be recovered or settled both no more and more than twelve months after reporting date [line items]    
Gross lease liabilities 190.1 245.8
Group cash pool participants    
Disclosure of amounts to be recovered or settled after twelve months for classes of assets and liabilities that contain amounts to be recovered or settled both no more and more than twelve months after reporting date [line items]    
Gross bank balances before cash pooling offset 57.7 112.6
Contingent liability for guarantees    
Disclosure of amounts to be recovered or settled after twelve months for classes of assets and liabilities that contain amounts to be recovered or settled both no more and more than twelve months after reporting date [line items]    
Estimated financial effect of contingent liabilities SFr 168.2 SFr 155.6