Consolidated Balance Sheets (Parenthetical) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013 USD ($)	Jun. 30, 2013 CHF	Dec. 31, 2012 USD ($)	Dec. 31, 2012 CHF
Statement of Financial Position [Abstract]
Fixed maturities available for sale, at amortized cost	$ 45,988		$ 44,666
Fixed maturities available for sale, hybrid financial instruments	276		309
Fixed maturities held to maturity, at amortized cost	6,762		7,633
Equity securities, at cost	843		707
Other investments, cost	2,543		2,465
Investments in partially-owned insurance companies, cost	$ 449		$ 451
Common Shares, par value		27.95		28.89
Common Shares, shares issued	342,832,412	342,832,412	342,832,412	342,832,412
Common Shares, shares outstanding	340,086,269	340,086,269	340,321,534	340,321,534
Common Shares in treasury, shares	2,746,143	2,746,143	2,510,878	2,510,878