Shareholders' equity (Details)			3 Months Ended	9 Months Ended
	Aug. 04, 2022 shares	Jan. 17, 2022 shares	Sep. 30, 2021 shares	Sep. 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				31,356,130		47,448,502
Treasury Stock, Shares, Retired	13,179,100	14,465,400		27,644,500
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures				2,470,600
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
Treasury Stock, Shares, Retired	13,179,100	14,465,400		27,644,500
Nov 2020 Stock Repurchase Plan
Stockholders' Equity Note [Abstract]
Number of shares repurchased			8,412,000