Shareholders' equity (Details)		3 Months Ended	6 Months Ended
	Jan. 17, 2022 shares	Jun. 30, 2021 shares	Jun. 30, 2022 SFr / shares shares	May 19, 2022 $ / shares	Dec. 31, 2021 SFr / shares shares	May 20, 2021 $ / shares	May 20, 2020 $ / shares
Stockholders' Equity Note [Abstract]
Common Shares, par value | SFr / shares			SFr 24.15		SFr 24.15
Common Shares in treasury, shares			41,081,627		47,448,502
Treasury Stock, Shares, Retired	14,465,400
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			2,247,675
Common Stock, Dividend Rate Approved | $ / shares				$ 0.83		$ 0.80	$ 0.78
Annual dividend per share approved by shareholders | $ / shares				3.32		3.20	3.12
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividend Rate Approved | $ / shares				$ 0.83		$ 0.80	$ 0.78
Nov 2020 Stock Repurchase Plan
Stockholders' Equity Note [Abstract]
Number of shares repurchased		11,355,400