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	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Document Period End Date	Sep. 30, 2015
Held to maturity, Amortized Cost	$ 8,564	$ 7,331
Held to maturity, Gross Unrealized Appreciation	235	266
Held to maturity, Gross Unrealized Depreciation	(49)	(8)
Held to maturity, Fair Value	8,750	7,589
Available for sale, Amortized Cost	47,411	47,826
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	1,472	1,871
Available for sale, Gross Unrealized Depreciation	(605)	(302)
Available for sale, Fair Value	48,278	49,395
Available for sale, OTTI recognized in AOCI	(21)	(8)
U.S. Treasury And Agency [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	756	832
Held to maturity, Gross Unrealized Appreciation	19	20
Held to maturity, Gross Unrealized Depreciation	(1)	(2)
Held to maturity, Fair Value	774	850
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	2,800	2,741
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	85	87
Available for sale, Gross Unrealized Depreciation	0	(8)
Available for sale, Fair Value	2,885	2,820
Available for sale, OTTI recognized in AOCI	0	0
Foreign [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	784	916
Held to maturity, Gross Unrealized Appreciation	38	47
Held to maturity, Gross Unrealized Depreciation	(4)	0
Held to maturity, Fair Value	818	963
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	13,976	14,703
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	523	629
Available for sale, Gross Unrealized Depreciation	(208)	(90)
Available for sale, Fair Value	14,291	15,242
Available for sale, OTTI recognized in AOCI	(6)	0
Corporate Securities [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	3,093	2,323
Held to maturity, Gross Unrealized Appreciation	74	102
Held to maturity, Gross Unrealized Depreciation	(41)	(2)
Held to maturity, Fair Value	3,126	2,423
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	16,790	16,897
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	467	704
Available for sale, Gross Unrealized Depreciation	(365)	(170)
Available for sale, Fair Value	16,892	17,431
Available for sale, OTTI recognized in AOCI	(14)	(7)
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	1,758	1,983
Held to maturity, Gross Unrealized Appreciation	60	57
Held to maturity, Gross Unrealized Depreciation	(1)	(1)
Held to maturity, Fair Value	1,817	2,039
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	10,858	10,011
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	286	304
Available for sale, Gross Unrealized Depreciation	(25)	(29)
Available for sale, Fair Value	11,119	10,286
Available for sale, OTTI recognized in AOCI	(1)	(1)
States, Municipalities, And Political Subdivisions [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	2,173	1,277
Held to maturity, Gross Unrealized Appreciation	44	40
Held to maturity, Gross Unrealized Depreciation	(2)	(3)
Held to maturity, Fair Value	2,215	1,314
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	2,987	3,474
AvailableforsaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments	111	147
Available for sale, Gross Unrealized Depreciation	(7)	(5)
Available for sale, Fair Value	3,091	3,616
Available for sale, OTTI recognized in AOCI	$ 0	$ 0