Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 2,150	$ 702
Less than 12 months, unrealized losses	(99)	(4)
12 months or longer, fair value	320	582
12 months or longer, unrealized losses	(86)	(148)
Total available-for-sale, fair value	2,470	1,284
Total available-for-sale, unrealized losses	(185)	(152)
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	0	297
Less than 12 months, unrealized losses	0	(19)
12 months or longer, fair value	1,174	1,287
12 months or longer, unrealized losses	(251)	(138)
Total held-to-maturity, fair value	1,174	1,584
Total held-to-maturity, unrealized losses	(251)	(157)
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value		0
Less than 12 months, unrealized losses		0
12 months or longer, fair value		31
12 months or longer, unrealized losses		(6)
Total available-for-sale, fair value		31
Total available-for-sale, unrealized losses		(6)
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	0	297
Less than 12 months, unrealized losses	0	(19)
12 months or longer, fair value	1,174	1,287
12 months or longer, unrealized losses	(251)	(138)
Total held-to-maturity, fair value	1,174	1,584
Total held-to-maturity, unrealized losses	(251)	(157)
Residential Mortgage Backed Non Agency [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value		0
Less than 12 months, unrealized losses		0
12 months or longer, fair value		82
12 months or longer, unrealized losses		(10)
Total available-for-sale, fair value		82
Total available-for-sale, unrealized losses		(10)
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value		0
Less than 12 months, unrealized losses		0
12 months or longer, fair value		85
12 months or longer, unrealized losses		(8)
Total available-for-sale, fair value		85
Total available-for-sale, unrealized losses		(8)
Other Asset Backed [Member] | Variable Interest Entity Primary Beneficiary [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value		0
Less than 12 months, unrealized losses		0
12 months or longer, fair value		0
12 months or longer, unrealized losses		0
Total available-for-sale, fair value		0
Total available-for-sale, unrealized losses		0
Perpetual Debt And Equity Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	4	1
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	0	1
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	4	2
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	2,146	701
Less than 12 months, unrealized losses	(99)	(4)
12 months or longer, fair value	320	383
12 months or longer, unrealized losses	(86)	(124)
Total available-for-sale, fair value	2,466	1,084
Total available-for-sale, unrealized losses	(185)	(128)
Fixed Maturities [Member] | U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	208	234
Less than 12 months, unrealized losses	(8)	(1)
12 months or longer, fair value	2	0
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	210	234
Total available-for-sale, unrealized losses	(8)	(1)
Fixed Maturities [Member] | US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	730	69
Less than 12 months, unrealized losses	(48)	0
12 months or longer, fair value	58	87
12 months or longer, unrealized losses	(4)	(12)
Total available-for-sale, fair value	788	156
Total available-for-sale, unrealized losses	(52)	(12)
Fixed Maturities [Member] | Foreign Government Debt [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	12	11
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	0	1
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	12	12
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member] | Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	610	202
Less than 12 months, unrealized losses	(23)	(2)
12 months or longer, fair value	20	57
12 months or longer, unrealized losses	(3)	(18)
Total available-for-sale, fair value	630	259
Total available-for-sale, unrealized losses	(26)	(20)
Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	528	173
Less than 12 months, unrealized losses	(18)	(1)
12 months or longer, fair value	32	38
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	560	211
Total available-for-sale, unrealized losses	(18)	(1)
Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	5	4
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	23	28
12 months or longer, unrealized losses	(6)	(8)
Total available-for-sale, fair value	28	32
Total available-for-sale, unrealized losses	(6)	(8)
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	22	3
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	1	27
12 months or longer, unrealized losses	0	(4)
Total available-for-sale, fair value	23	30
Total available-for-sale, unrealized losses	(1)	(4)
Fixed Maturities [Member] | Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	9	1
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	128	80
12 months or longer, unrealized losses	(56)	(71)
Total available-for-sale, fair value	137	81
Total available-for-sale, unrealized losses	(57)	(71)
Fixed Maturities [Member] | Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	22	4
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	56	65
12 months or longer, unrealized losses	(17)	(11)
Total available-for-sale, fair value	78	69
Total available-for-sale, unrealized losses	$ (17)	$ (11)