Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 417	$ 2,389
Less than 12 months, unrealized losses	(2)	(36)
12 months or longer, fair value	360	413
12 months or longer, unrealized losses	(97)	(136)
Total available-for-sale, fair value	777	2,802
Total available-for-sale, unrealized losses	(99)	(172)
Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	297	1,093
Less than 12 months, unrealized losses	(18)	(17)
12 months or longer, fair value	212	280
12 months or longer, unrealized losses	(363)	(295)
Total held-to-maturity, fair value	509	1,373
Total held-to-maturity, unrealized losses	(381)	(312)
Corporate Obligations [Member] \| Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	297	1,093
Less than 12 months, unrealized losses	(18)	(17)
12 months or longer, fair value	212	280
12 months or longer, unrealized losses	(363)	(295)
Total held-to-maturity, fair value	509	1,373
Total held-to-maturity, unrealized losses	(381)	(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	417	2,387
Less than 12 months, unrealized losses	(2)	(36)
12 months or longer, fair value	359	410
12 months or longer, unrealized losses	(97)	(136)
Total available-for-sale, fair value	776	2,797
Total available-for-sale, unrealized losses	(99)	(172)
Fixed Maturities [Member] \| U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	27	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	27	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	7	536
Less than 12 months, unrealized losses	0	(11)
12 months or longer, fair value	17	42
12 months or longer, unrealized losses	(2)	(3)
Total available-for-sale, fair value	24	578
Total available-for-sale, unrealized losses	(2)	(14)
Fixed Maturities [Member] \| Foreign Government Debt [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	3	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	5	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	152	693
Less than 12 months, unrealized losses	0	(14)
12 months or longer, fair value	62	78
12 months or longer, unrealized losses	(79)	(89)
Total available-for-sale, fair value	214	771
Total available-for-sale, unrealized losses	(79)	(103)
Fixed Maturities [Member] \| Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	61	399
Less than 12 months, unrealized losses	0	(4)
12 months or longer, fair value	144	159
12 months or longer, unrealized losses	(1)	(5)
Total available-for-sale, fair value	205	558
Total available-for-sale, unrealized losses	(1)	(9)
Fixed Maturities [Member] \| Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	9	24
Less than 12 months, unrealized losses	(1)	(2)
12 months or longer, fair value	29	17
12 months or longer, unrealized losses	(6)	(4)
Total available-for-sale, fair value	38	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	21	25
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	4	1
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	25	26
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member] \| Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	4	2
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	20	29
12 months or longer, unrealized losses	0	(18)
Total available-for-sale, fair value	24	31
Total available-for-sale, unrealized losses	0	(18)
Fixed Maturities [Member] \| Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	133	242
Less than 12 months, unrealized losses	(1)	(1)
12 months or longer, fair value	81	34
12 months or longer, unrealized losses	(8)	(16)
Total available-for-sale, fair value	214	276
Total available-for-sale, unrealized losses	$ (9)	$ (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.

+ References

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-Publisher FASB
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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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