Shareholders' equity (Details)			6 Months Ended
	Mar. 07, 2025 shares	May 21, 2024 shares	Jun. 30, 2025 SFr / shares shares	May 15, 2025 $ / shares	Dec. 31, 2024 SFr / shares shares	May 16, 2024 $ / shares	May 17, 2023 $ / shares
Stockholders' Equity Note [Abstract]
Common Shares, par value | SFr / shares			SFr 0.50		SFr 0.50
Treasury Stock, Shares, Retired | shares	7,518,565	11,825,600	7,518,565
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures | shares			1,642,634
Common Stock, Dividend Rate Approved | $ / shares				$ 0.97		$ 0.91	$ 0.86
Annual dividend per share approved by shareholders | $ / shares				3.88		3.64	3.44
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividend Rate Approved | $ / shares				0.97		0.91	0.86
Treasury Stock, Shares, Retired | shares	7,518,565	11,825,600	7,518,565
Treasury Stock, Common, Shares | shares			13,446,633		18,922,323
Common Shares, par value | SFr / shares			SFr 0.50		SFr 0.50
Annual dividend per share approved by shareholders | $ / shares				$ 3.88		$ 3.64	$ 3.44