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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | $ 6,160 | $ 6,509
Gross unrealized gains |  | 132 | 209
Gross unrealized losses |  | (172) | (147)
Total available-for-sale, fair value |  | 6,120 | 6,571
Other-than-temporary impairments | [1] | (89) | (90)
Held To Maturity Securities [Abstract] |  |  |
Amortized cost |  | 2,689 | 2,757
Gross unrealized gains |  | 24 | 77
Gross unrealized losses |  | (312) | (202)
Total Held-To-Maturity, fair value |  | 2,401 | 2,632
Other-Than-Temporary Impairments | [1] | 0 | 0
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Held To Maturity Securities [Abstract] |  |  |
Amortized cost |  | 2,689 | 2,757
Gross unrealized gains |  | 24 | 77
Gross unrealized losses |  | (312) | (202)
Total Held-To-Maturity, fair value |  | 2,401 | 2,632
Other-Than-Temporary Impairments | [1] | 0 | 0
Money Market Securities [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 351 | 422
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 351 | 422
Other-than-temporary impairments | [1] | 0 | 0
Perpetual Debt And Equity Securities [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 12 | 12
Gross unrealized gains |  | 1 | 1
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 13 | 13
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 5,797 | 6,075
Gross unrealized gains |  | 131 | 208
Gross unrealized losses |  | (172) | (147)
Total available-for-sale, fair value |  | 5,756 | 6,136
Other-than-temporary impairments | [1] | (89) | (90)
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Held To Maturity Securities [Abstract] |  |  |
Amortized cost |  | 2,689 |
Total Held-To-Maturity, fair value |  | 2,401 |
Fixed Maturities [Member] | U S Treasury And Government [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 947 | 631
Gross unrealized gains |  | 32 | 39
Gross unrealized losses |  | (3) | (3)
Total available-for-sale, fair value |  | 976 | 667
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | US States And Political Subdivisions [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 1,674 | 1,644
Gross unrealized gains |  | 65 | 94
Gross unrealized losses |  | (14) | (8)
Total available-for-sale, fair value |  | 1,725 | 1,730
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Foreign Governments [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 197 | 283
Gross unrealized gains |  | 3 | 7
Gross unrealized losses |  | (2) | 0
Total available-for-sale, fair value |  | 198 | 290
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Corporate Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 1,516 | 1,984
Gross unrealized gains |  | 21 | 44
Gross unrealized losses |  | (103) | (92)
Total available-for-sale, fair value |  | 1,434 | 1,936
Other-than-temporary impairments | [1] | (85) | (86)
Fixed Maturities [Member] | Residential Mortgage-Backed Agency [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 995 | 1,116
Gross unrealized gains |  | 7 | 17
Gross unrealized losses |  | (9) | (7)
Total available-for-sale, fair value |  | 993 | 1,126
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Residential Mortgage-Backed Non-Agency [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 55 | 54
Gross unrealized gains |  | 2 | 3
Gross unrealized losses |  | (6) | (4)
Total available-for-sale, fair value |  | 51 | 53
Other-than-temporary impairments | [1] | (4) | (4)
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 31 | 19
Gross unrealized gains |  | 0 | 1
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 31 | 20
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 51 | 113
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | (18) | (21)
Total available-for-sale, fair value |  | 33 | 92
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Other Asset-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 331 | 231
Gross unrealized gains |  | 1 | 3
Gross unrealized losses |  | (17) | (12)
Total available-for-sale, fair value |  | 315 | 222
Other-than-temporary impairments | [1] | $ 0 | $ 0
[1] | Represents unrealized gains or losses on other than temporarily impaired securities recognized in AOCI, which includes the non-credit component of impairments, as well as all subsequent changes in fair value of such impaired securities reported in AOCI.

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