Investments (Schedule Of Components Of Restricted Assets) (Details) (USD $)	Dec. 31, 2011		Dec. 31, 2010
Investments [Abstract]
Trust funds	$ 9,940,000,000		$ 8,200,000,000
Deposits with non-U.S. regulatory authorities	2,240,000,000		2,289,000,000
Deposits with U.S. regulatory authorities	1,307,000,000		1,384,000,000
Other pledged assets	1,615,000,000	[1]	1,190,000,000	[1]
Total restricted assets	15,102,000,000		13,063,000,000
Restricted assets	$ 1,300,000,000		$ 1,000,000,000

[1] Includes restricted assets of $1.3 billion and $1.0 billion at December 31, 2011 and 2010, respectively, pledged under reverse repurchase agreements.