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	Sep. 30, 2014	Dec. 31, 2013
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	$ 10,464	$ 18,228
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(128)	(652)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	5,436	894
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(136)	(63)
Investment securities, Unrealized loss position, Total Fair Value	15,900	19,122
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(264)	(715)
US Treasury and Government [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	439	1,794
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(2)	(57)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	943	31
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(20)	(6)
Investment securities, Unrealized loss position, Total Fair Value	1,382	1,825
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(22)	(63)
Foreign Government Debt Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	2,420	4,621
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(34)	(114)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	916	201
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(19)	(8)
Investment securities, Unrealized loss position, Total Fair Value	3,336	4,822
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(53)	(122)
Corporate Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	4,943	3,836
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(72)	(118)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	854	194
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(25)	(14)
Investment securities, Unrealized loss position, Total Fair Value	5,797	4,030
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(97)	(132)
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	2,206	5,248
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(11)	(197)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	2,050	384
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(64)	(31)
Investment securities, Unrealized loss position, Total Fair Value	4,256	5,632
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(75)	(228)
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	311	2,164
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(1)	(90)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	673	84
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(8)	(4)
Investment securities, Unrealized loss position, Total Fair Value	984	2,248
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(9)	(94)
Fixed Maturities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	10,319	17,663
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(120)	(576)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value	5,436	894
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss	(136)	(63)
Investment securities, Unrealized loss position, Total Fair Value	15,755	18,557
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(256)	(639)
Equity Securities [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	67	498
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(5)	(67)
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	67	498
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	(5)	(67)
Other Long-term Investments [Member]
Investment [Line Items]
Investment securities, Unrealized loss position, 0-12 Months, Fair Value	78	67
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss	(3)	(9)
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	78	67
Investment securities, Unrealized loss position, Total Gross Unrealized Loss	$ (3)	$ (9)