Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 750	$ 2,389
Less than 12 months, unrealized losses	(10)	(36)
12 months or longer, fair value	456	413
12 months or longer, unrealized losses	(131)	(136)
Total available-for-sale, fair value	1,206	2,802
Total available-for-sale, unrealized losses	(141)	(172)
Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	289	1,093
Less than 12 months, unrealized losses	(26)	(17)
12 months or longer, fair value	236	280
12 months or longer, unrealized losses	(339)	(295)
Total held-to-maturity, fair value	525	1,373
Total held-to-maturity, unrealized losses	(365)	(312)
Corporate Obligations [Member] \| Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	289	1,093
Less than 12 months, unrealized losses	(26)	(17)
12 months or longer, fair value	236	280
12 months or longer, unrealized losses	(339)	(295)
Total held-to-maturity, fair value	525	1,373
Total held-to-maturity, unrealized losses	(365)	(312)
Perpetual Debt And Equity Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	0	2
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	1	3
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	1	5
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	750	2,387
Less than 12 months, unrealized losses	(10)	(36)
12 months or longer, fair value	455	410
12 months or longer, unrealized losses	(131)	(136)
Total available-for-sale, fair value	1,205	2,797
Total available-for-sale, unrealized losses	(141)	(172)
Fixed Maturities [Member] \| U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	53	434
Less than 12 months, unrealized losses	0	(2)
12 months or longer, fair value	0	50
12 months or longer, unrealized losses	0	(1)
Total available-for-sale, fair value	53	484
Total available-for-sale, unrealized losses	0	(3)
Fixed Maturities [Member] \| US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	115	536
Less than 12 months, unrealized losses	(1)	(11)
12 months or longer, fair value	20	42
12 months or longer, unrealized losses	(2)	(3)
Total available-for-sale, fair value	135	578
Total available-for-sale, unrealized losses	(3)	(14)
Fixed Maturities [Member] \| Foreign Government Debt [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	10	32
Less than 12 months, unrealized losses	0	(2)
12 months or longer, fair value	2	0
12 months or longer, unrealized losses	(1)	0
Total available-for-sale, fair value	12	32
Total available-for-sale, unrealized losses	(1)	(2)
Fixed Maturities [Member] \| Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	303	693
Less than 12 months, unrealized losses	(4)	(14)
12 months or longer, fair value	83	78
12 months or longer, unrealized losses	(92)	(89)
Total available-for-sale, fair value	386	771
Total available-for-sale, unrealized losses	(96)	(103)
Fixed Maturities [Member] \| Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	58	399
Less than 12 months, unrealized losses	0	(4)
12 months or longer, fair value	259	159
12 months or longer, unrealized losses	(3)	(5)
Total available-for-sale, fair value	317	558
Total available-for-sale, unrealized losses	(3)	(9)
Fixed Maturities [Member] \| Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	18	24
Less than 12 months, unrealized losses	(2)	(2)
12 months or longer, fair value	21	17
12 months or longer, unrealized losses	(5)	(4)
Total available-for-sale, fair value	39	41
Total available-for-sale, unrealized losses	(7)	(6)
Fixed Maturities [Member] \| Commercial Mortgage Backed Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	22	25
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	1	1
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	23	26
Total available-for-sale, unrealized losses	(1)	0
Fixed Maturities [Member] \| Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	2	2
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	25	29
12 months or longer, unrealized losses	(17)	(18)
Total available-for-sale, fair value	27	31
Total available-for-sale, unrealized losses	(17)	(18)
Fixed Maturities [Member] \| Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	169	242
Less than 12 months, unrealized losses	(2)	(1)
12 months or longer, fair value	44	34
12 months or longer, unrealized losses	(11)	(16)
Total available-for-sale, fair value	213	276
Total available-for-sale, unrealized losses	$ (13)	$ (17)

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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