Shareholders' equity Schedule of Dividends Declared (Details)	12 Months Ended
	Dec. 31, 2020 SFr / shares	Dec. 31, 2020 $ / shares	Dec. 31, 2019 SFr / shares	Dec. 31, 2019 $ / shares	Dec. 31, 2018 SFr / shares	Dec. 31, 2018 $ / shares
Switzerland, Francs
Dividends Declared [Line Items]
Total dividend distributions per common share | SFr / shares	SFr 2.89		SFr 2.94		SFr 2.84
United States of America, Dollars
Dividends Declared [Line Items]
Total dividend distributions per common share | $ / shares		$ 3.09		$ 2.98		$ 2.90