Investments (Schedule Of Amortized Cost And Fair Value Of Fixed Maturities And Related Other-Than-Temporary Impairment Recognized In Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Document Period End Date	Mar. 31, 2016
Held to maturity, Amortized Cost	$ 11,280	$ 8,430
Held to maturity, Gross Unrealized Appreciation	323	190
Held to maturity, Gross Unrealized Depreciation	(23)	(68)
Held to maturity, Fair Value	11,580	8,552
Available for sale, Amortized Cost	75,991	43,149
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	1,899	1,168
Available for sale, Gross Unrealized Depreciation	(352)	(730)
Available for sale, Fair Value	77,538	43,587
Available for sale, OTTI recognized in AOCI	(38)	(42)
U.S. Treasury And Agency [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	700	733
Held to maturity, Gross Unrealized Appreciation	23	13
Held to maturity, Gross Unrealized Depreciation	0	(1)
Held to maturity, Fair Value	723	745
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	2,984	2,481
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	85	52
Available for sale, Gross Unrealized Depreciation	0	(5)
Available for sale, Fair Value	3,069	2,528
Available for sale, OTTI recognized in AOCI	0	0
Foreign [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	749	763
Held to maturity, Gross Unrealized Appreciation	38	30
Held to maturity, Gross Unrealized Depreciation	(4)	(8)
Held to maturity, Fair Value	783	785
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	20,026	13,190
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	685	468
Available for sale, Gross Unrealized Depreciation	(118)	(213)
Available for sale, Fair Value	20,593	13,445
Available for sale, OTTI recognized in AOCI	(16)	(13)
Corporate [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	2,951	3,054
Held to maturity, Gross Unrealized Appreciation	98	57
Held to maturity, Gross Unrealized Depreciation	(16)	(55)
Held to maturity, Fair Value	3,033	3,056
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	21,783	15,028
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	640	355
Available for sale, Gross Unrealized Depreciation	(212)	(454)
Available for sale, Fair Value	22,211	14,929
Available for sale, OTTI recognized in AOCI	(21)	(28)
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	1,652	1,707
Held to maturity, Gross Unrealized Appreciation	65	38
Held to maturity, Gross Unrealized Depreciation	(1)	(2)
Held to maturity, Fair Value	1,716	1,743
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	11,766	9,827
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	289	183
Available for sale, Gross Unrealized Depreciation	(10)	(52)
Available for sale, Fair Value	12,045	9,958
Available for sale, OTTI recognized in AOCI	(1)	(1)
States, Municipalities, And Political Subdivisions [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	5,228	2,173
Held to maturity, Gross Unrealized Appreciation	99	52
Held to maturity, Gross Unrealized Depreciation	(2)	(2)
Held to maturity, Fair Value	5,325	2,223
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	19,432	2,623
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	200	110
Available for sale, Gross Unrealized Depreciation	(12)	(6)
Available for sale, Fair Value	19,620	2,727
Available for sale, OTTI recognized in AOCI	$ 0	$ 0