Investments (Schedule Of Components Of Restricted Assets) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Trust funds	$ 11,421	$ 11,389
Deposits with non-U.S. regulatory authorities	2,100	2,133
Assets pledged under repurchase agreements	1,402	1,401
Deposits with U.S. regulatory authorities	1,322	1,338
Other pledged assets	426	456
Total restricted assets	$ 16,671	$ 16,717