Investments (Schedule Of Components Of Restricted Assets) (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Funds Held under Reinsurance Agreements, Asset	$ 13,880	$ 11,862
Deposits with non-U.S. regulatory authorities	2,191	2,075
Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements	1,461	1,459
Deposits with U.S. regulatory authorities	2,203	1,242
Other pledged assets	435	392
Total restricted assets	$ 20,170	$ 17,030