Consolidated Balance Sheets (Parenthetical) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012 USD ($)	Dec. 31, 2012 CHF	Dec. 31, 2011 USD ($)	Dec. 31, 2011 CHF
Statement of Financial Position [Abstract]
Fixed maturities available for sale, at amortized cost	$ 44,666		$ 40,450
Fixed maturities available for sale, hybrid financial instruments	309		357
Fixed maturities held to maturity, at amortized cost	7,633		8,605
Equity securities, at cost	707		671
Other investments, cost	2,465		2,112
Investments in partially-owned insurance companies, cost	$ 451		$ 345
Common Shares, par value		28.89		30.27
Common Shares, shares issued	342,832,412	342,832,412	342,832,412	342,832,412
Common Shares, shares outstanding	340,321,534	340,321,534	336,927,276	336,927,276
Common Shares in treasury, shares	2,510,878	2,510,878	5,905,136	5,905,136