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	Sep. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Held to maturity, Amortized Cost	$ 10,927	$ 8,430
Held to maturity, Gross Unrealized Appreciation	441	190
Held to maturity, Gross Unrealized Depreciation	(2)	(68)
Held to maturity, at Fair Value	11,366	8,552
U.S. Treasury And Agency [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	709	733
Held to maturity, Gross Unrealized Appreciation	26	13
Held to maturity, Gross Unrealized Depreciation	0	(1)
Held to maturity, at Fair Value	735	745
Held to maturity, OTTI recognized in AOCI	0	0
Foreign [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	694	763
Held to maturity, Gross Unrealized Appreciation	45	30
Held to maturity, Gross Unrealized Depreciation	0	(8)
Held to maturity, at Fair Value	739	785
Held to maturity, OTTI recognized in AOCI	0	0
Corporate [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	2,852	3,054
Held to maturity, Gross Unrealized Appreciation	131	57
Held to maturity, Gross Unrealized Depreciation	(2)	(55)
Held to maturity, at Fair Value	2,981	3,056
Held to maturity, OTTI recognized in AOCI	0	0
Collateralized Mortgage Backed Securities [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	1,507	1,707
Held to maturity, Gross Unrealized Appreciation	72	38
Held to maturity, Gross Unrealized Depreciation	0	(2)
Held to maturity, at Fair Value	1,579	1,743
Held to maturity, OTTI recognized in AOCI	0	0
States, Municipalities, And Political Subdivisions [Member]
Investment [Line Items]
Held to maturity, Amortized Cost	5,165	2,173
Held to maturity, Gross Unrealized Appreciation	167	52
Held to maturity, Gross Unrealized Depreciation	0	(2)
Held to maturity, at Fair Value	5,332	2,223
Held to maturity, OTTI recognized in AOCI	$ 0	$ 0