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, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	$ 350	$ 367
Held to maturity, Gross Unrealized Depreciation	(4)	(4)
Held to maturity, Fair Value	7,213	7,633
Held to maturity, OTTI recognized in AOCI
Available for sale, Amortized Cost	45,470	44,666
Available for sale, Gross Unrealized Appreciation	2,557	2,725
Available for sale, Gross Unrealized Depreciation	(80)	(85)
Available for sale, Fair Value	47,947	47,306
Available for sale, OTTI recognized in AOCI	(45)	(91)
Held to maturity, Amortized Cost	6,867	7,270
U.S. Treasury And Agency [Member]
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	35	39
Held to maturity, Gross Unrealized Depreciation	0	0
Held to maturity, Fair Value	997	1,083
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	3,690	3,553
Available for sale, Gross Unrealized Appreciation	158	183
Available for sale, Gross Unrealized Depreciation	(5)	(1)
Available for sale, Fair Value	3,843	3,735
Available for sale, OTTI recognized in AOCI	0	0
Held to maturity, Amortized Cost	962	1,044
Foreign [Member]
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	55	54
Held to maturity, Gross Unrealized Depreciation	0	0
Held to maturity, Fair Value	937	964
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	13,007	13,016
Available for sale, Gross Unrealized Appreciation	673	711
Available for sale, Gross Unrealized Depreciation	(16)	(14)
Available for sale, Fair Value	13,664	13,713
Available for sale, OTTI recognized in AOCI	0	0
Held to maturity, Amortized Cost	882	910
Corporate Securities [Member]
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	138	142
Held to maturity, Gross Unrealized Depreciation	0	0
Held to maturity, Fair Value	2,202	2,275
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	15,769	15,529
Available for sale, Gross Unrealized Appreciation	1,180	1,210
Available for sale, Gross Unrealized Depreciation	(28)	(31)
Available for sale, Fair Value	16,921	16,708
Available for sale, OTTI recognized in AOCI	(6)	(7)
Held to maturity, Amortized Cost	2,064	2,133
Mortgage Backed-Securities [Member]
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	81	88
Held to maturity, Gross Unrealized Depreciation	0	0
Held to maturity, Fair Value	1,893	2,116
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	9,813	10,051
Available for sale, Gross Unrealized Appreciation	384	458
Available for sale, Gross Unrealized Depreciation	(26)	(36)
Available for sale, Fair Value	10,171	10,473
Available for sale, OTTI recognized in AOCI	(39)	(84)
Held to maturity, Amortized Cost	1,812	2,028
States, Municipalities, And Political Subdivisions [Member]
Investment [Line Items]
Held to maturity, Gross Unrealized Appreciation	41	44
Held to maturity, Gross Unrealized Depreciation	(4)	(4)
Held to maturity, Fair Value	1,184	1,195
Held to maturity, OTTI recognized in AOCI	0	0
Available for sale, Amortized Cost	3,191	2,517
Available for sale, Gross Unrealized Appreciation	162	163
Available for sale, Gross Unrealized Depreciation	(5)	(3)
Available for sale, Fair Value	3,348	2,677
Available for sale, OTTI recognized in AOCI	0	0
Held to maturity, Amortized Cost	$ 1,147	$ 1,155