Shareholders' equity Shareholders' equity (Details)	3 Months Ended				9 Months Ended							3 Months Ended	9 Months Ended		1 Months Ended
	Sep. 30, 2014 USD ($)	Sep. 30, 2014 CHF	Sep. 30, 2013 USD ($)	Sep. 30, 2013 CHF	Sep. 30, 2014 USD ($)	Sep. 30, 2014 CHF	Sep. 30, 2013 USD ($)	Sep. 30, 2013 CHF	May 31, 2014 USD ($)	Dec. 31, 2013 CHF	May 31, 2013 USD ($)	Sep. 30, 2014 November 2013 Stock Repurchase Plan [Member] USD ($)	Sep. 30, 2014 November 2013 Stock Repurchase Plan [Member] USD ($)	Nov. 30, 2013 November 2013 Stock Repurchase Plan [Member] USD ($)	Oct. 28, 2014 November 2013 Stock Repurchase Plan [Member] Subsequent Event [Member] USD ($)
Equity, Class of Treasury Stock [Line Items]
Share repurchase amount												$ 450,000,000	$ 1,019,000,000		$ 74,000,000
Repurchase of outstanding common shares, shares												4,349,302	10,143,184		699,965
Share repurchase authorization remains												924,000,000	924,000,000		850,000,000
Common Shares in treasury, shares	10,720,855	10,720,855			10,720,855	10,720,855				3,038,477
Stock repurchase program, authorized amount														$ 2,000,000,000
Annual dividend per share approved by shareholders									$ 2.60		$ 2.04
Dividends Declared From Additional Paid In Capital					$ 0.24	0.20
Increase to dividend approved by shareholders in January					$ 0.12
Dividends declared per common share					$ 2.05	1.84
Par Value Reduction	$ 0.65	0.61	$ 0.51	0.46	$ 1.81	1.64	$ 1.51	1.40
Common Shares, par value		25.40				25.40				27.04