Shareholders' equity (Details)		3 Months Ended
	May 22, 2023 shares	Mar. 31, 2024 SFr / shares shares	Dec. 31, 2023 SFr / shares shares	May 17, 2023 $ / shares	May 19, 2022 $ / shares
Stockholders' Equity Note [Abstract]
Common Shares, par value | SFr / shares		SFr 0.50	SFr 0.50
Treasury Stock, Shares, Retired	14,925,028	14,925,028
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		1,983,550
Common Stock, Dividend Rate Approved | $ / shares				$ 0.86	$ 0.83
Annual dividend per share approved by shareholders | $ / shares				3.44	3.32
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividend Rate Approved | $ / shares				$ 0.86	$ 0.83
Treasury Stock, Shares, Retired	14,925,028	14,925,028
Treasury Stock, Common, Shares		25,418,520	26,181,949
Common Shares, par value | SFr / shares		SFr 0.50	SFr 0.50