Shareholders' equity Dividends Declared (Details)	3 Months Ended				9 Months Ended
	Sep. 30, 2020 $ / shares	Sep. 30, 2020 SFr / shares	Sep. 30, 2019 $ / shares	Sep. 30, 2019 SFr / shares	Sep. 30, 2020 $ / shares	Sep. 30, 2020 SFr / shares	Sep. 30, 2019 $ / shares	Sep. 30, 2019 SFr / shares	May 20, 2020 $ / shares	May 31, 2019 $ / shares	May 31, 2018 $ / shares
Equity, Class of Treasury Stock [Line Items]
Annual dividend per share approved by shareholders									$ 3.12	$ 3.00	$ 2.92
Common Stock, Dividend Rate Approved									$ 0.78	$ 0.75	$ 0.73
United States of America, Dollars
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.78		$ 0.75		$ 2.31		$ 2.23
Switzerland, Francs
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividends, Per Share, Declared | SFr / shares		SFr 0.71		SFr 0.73		SFr 2.18		SFr 2.20