Business developments - Share transactions (Details 2) - CHF (SFr)
SFr in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Jun. 30, 2020
Dec. 31, 2018
Additional share information          
Issuance of common shares 203,000,000 0 0    
Issued shares (in shares) 2,650,747,720 2,447,747,720 2,556,011,720   2,556,011,720
Series A MCNs [Member]          
Additional share information          
Issuance of common shares 100,000,000        
MCNs principal amount       SFr 865  
Series B MCNs [Member]          
Additional share information          
Issuance of common shares 103,000,000        
MCNs principal amount       SFr 891