Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	$ 16,679	$ 8,559
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(394)	(244)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	1,512	3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(62)	(79)
Investment securities, Unrealized loss position, Total Fair Value	18,191	12,491
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(456)	(323)
U.S. Treasury And Agency [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	693	350
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(5)	(1)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	137	666
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(1)	(9)
Investment securities, Unrealized loss position, Total Fair Value	830	1,016
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(6)	(10)
Foreign [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	3,867	2,262
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(104)	(75)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	273	375
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(12)	(15)
Investment securities, Unrealized loss position, Total Fair Value	4,140	2,637
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(116)	(90)
Corporate Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	6,361	4,684
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(195)	(150)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	520	738
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(32)	(22)
Investment securities, Unrealized loss position, Total Fair Value	6,881	5,422
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(227)	(172)
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	3,430	704
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(46)	(2)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	495	1,663
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(15)	(28)
Investment securities, Unrealized loss position, Total Fair Value	3,925	2,367
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(61)	(30)
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	2,215	458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(30)	(3)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	87	490
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(2)	(5)
Investment securities, Unrealized loss position, Total Fair Value	2,302	948
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(32)	(8)
Fixed Maturities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	16,566	8,458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(380)	(231)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	1,512	3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(62)	(79)
Investment securities, Unrealized loss position, Total Fair Value	18,078	12,390
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(442)	(310)
Equity Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	80	101
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(12)	(13)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	0	0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	0	0
Investment securities, Unrealized loss position, Total Fair Value	80	101
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(12)	$ (13)
Other Long-term Investments [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	33
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(2)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	0
Investment securities, Unrealized loss position, Total Fair Value	33
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	$ (2)