Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Investment [Line Items]
Document Period End Date	Mar. 31, 2015
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	$ 6,253	$ 8,559
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(169)	(244)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	1,607	3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(38)	(79)
Investment securities, Unrealized loss position, Total Fair Value	7,860	12,491
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(207)	(323)
US Treasury and Government [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	443	350
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(1)	(1)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	141	666
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(1)	(9)
Investment securities, Unrealized loss position, Total Fair Value	584	1,016
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(2)	(10)
Foreign Government Debt Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	1,747	2,262
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(64)	(75)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	317	375
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(12)	(15)
Investment securities, Unrealized loss position, Total Fair Value	2,064	2,637
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(76)	(90)
Corporate Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	2,140	4,684
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(79)	(150)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	500	738
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(15)	(22)
Investment securities, Unrealized loss position, Total Fair Value	2,640	5,422
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(94)	(172)
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	1,301	704
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(6)	(2)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	560	1,663
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(8)	(28)
Investment securities, Unrealized loss position, Total Fair Value	1,861	2,367
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(14)	(30)
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	462	458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(3)	(3)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	89	490
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(2)	(5)
Investment securities, Unrealized loss position, Total Fair Value	551	948
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(5)	(8)
Fixed Maturities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	6,093	8,458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(153)	(231)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	1,607	3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(38)	(79)
Investment securities, Unrealized loss position, Total Fair Value	7,700	12,390
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(191)	(310)
Equity Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	68	101
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(10)	(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	68	101
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(10)	(13)
Other Long-term Investments [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	92
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(6)
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	92
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	$ (6)