Shareholders' equity Dividends Declared (Details)	3 Months Ended
	Mar. 31, 2020 $ / shares	Mar. 31, 2020 SFr / shares	Mar. 31, 2019 $ / shares	Mar. 31, 2019 SFr / shares	May 31, 2019 $ / shares	May 31, 2018 $ / shares
Equity, Class of Treasury Stock [Line Items]
Annual dividend per share approved by shareholders					$ 3.00	$ 2.92
Common Stock, Dividend Rate Approved					$ 0.75	$ 0.73
United States of America, Dollars
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.75		$ 0.73
Switzerland, Francs
Equity, Class of Treasury Stock [Line Items]
Common Stock, Dividends, Per Share, Declared | SFr / shares		SFr 0.72		SFr 0.72