Shareholders' Equity (Narrative) (Details) In Thousands, except Share data, unless otherwise specified	9 Months Ended				0 Months Ended		0 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 CHF	Dec. 31, 2011	Jul. 30, 2012 Nonvoting Common Stock [Member]	Sep. 30, 2012 Nonvoting Common Stock [Member]	Jul. 30, 2012 Voting Common Stock [Member]	Sep. 30, 2012 Voting Common Stock [Member]	Sep. 30, 2011 American International Group Inc [Member] USD ($)
Class of Warrant or Right [Line Items]
Warrant agreements to acquire common shares	5,500,000								2,000,000
Warrants, exercise price per share	34.20								34.20
Repurchase of warrant	$ 0	$ 53,620							$ 53,620
Class of Stock [Line Items]
Common shares, outstanding	35,402,558			37,742,131		0		35,402,558
Shares cancelled, shares	2,919,900				173,100		2,236,900	419,900
Maximum percent increase in share capital authorized	20.00%
Maximum authorized value increase of registered share capital			97,359
Maximum authorized increased voting shares								7,500,728
Maximum number of conditional capital voting shares								5,200,000