Consolidated Balance Sheets (Parenthetical) In Millions, except Share data, unless otherwise specified	Mar. 31, 2012 USD ($)	Mar. 31, 2012 CHF	Dec. 31, 2011 USD ($)	Dec. 31, 2011 CHF
Consolidated Balance Sheets [Abstract]
Fixed maturities available for sale, at amortized cost	$ 41,661		$ 40,450
Fixed maturities available for sale, hybrid financial instruments	400		357
Fixed maturities held to maturity, at fair value	8,348		8,605
Equity securities, at cost	662		671
Other investments, cost	2,221		2,112
Investments in partially-owned insurance companies, cost	$ 339		$ 345
Common Shares, par value		30.27		30.27
Common Shares, shares issued	342,832,412	342,832,412	342,832,412	342,832,412
Common Shares, shares outstanding	338,653,382	338,653,382	336,927,276	336,927,276
Common Shares in treasury, shares	4,179,030	4,179,030	5,905,136	5,905,136