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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions | Sep. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | $ 6,265 | $ 6,509
Gross unrealized gains |  | 176 | 209
Gross unrealized losses |  | (158) | (147)
Total available-for-sale, fair value |  | 6,283 | 6,571
Other-than-temporary impairments | [1] | (92) | (90)
Held To Maturity Securities [Abstract] |  |  |
Amortized cost |  | 2,707 | 2,757
Gross unrealized gains |  | 12 | 77
Gross unrealized losses |  | (277) | (202)
Total Held-To-Maturity, fair value |  | 2,442 | 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 |  | 2,707 | 2,757
Gross unrealized gains |  | 12 | 77
Gross unrealized losses |  | (277) | (202)
Total Held-To-Maturity, fair value |  | 2,442 | 2,632
Other-Than-Temporary Impairments | [1] | 0 | 0
Money Market Securities [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 111 | 422
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 111 | 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 |  | 6,142 | 6,075
Gross unrealized gains |  | 175 | 208
Gross unrealized losses |  | (158) | (147)
Total available-for-sale, fair value |  | 6,159 | 6,136
Other-than-temporary impairments | [1] | (92) | (90)
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Held To Maturity Securities [Abstract] |  |  |
Amortized cost |  | 2,707 |
Total Held-To-Maturity, fair value |  | 2,442 |
Fixed Maturities [Member] | U S Treasury And Government [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 818 | 631
Gross unrealized gains |  | 39 | 39
Gross unrealized losses |  | (1) | (3)
Total available-for-sale, fair value |  | 856 | 667
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | US States And Political Subdivisions [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 1,779 | 1,644
Gross unrealized gains |  | 83 | 94
Gross unrealized losses |  | (11) | (8)
Total available-for-sale, fair value |  | 1,851 | 1,730
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Foreign Governments [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 212 | 283
Gross unrealized gains |  | 3 | 7
Gross unrealized losses |  | (2) | 0
Total available-for-sale, fair value |  | 213 | 290
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Corporate Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 1,772 | 1,984
Gross unrealized gains |  | 31 | 44
Gross unrealized losses |  | (104) | (92)
Total available-for-sale, fair value |  | 1,699 | 1,936
Other-than-temporary impairments | [1] | (88) | (86)
Fixed Maturities [Member] | Residential Mortgage-Backed Agency [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 1,034 | 1,116
Gross unrealized gains |  | 14 | 17
Gross unrealized losses |  | (5) | (7)
Total available-for-sale, fair value |  | 1,043 | 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 |  | 58 | 54
Gross unrealized gains |  | 3 | 3
Gross unrealized losses |  | (5) | (4)
Total available-for-sale, fair value |  | 56 | 53
Other-than-temporary impairments | [1] | (4) | (4)
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 16 | 19
Gross unrealized gains |  | 0 | 1
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 16 | 20
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 82 | 113
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | (20) | (21)
Total available-for-sale, fair value |  | 62 | 92
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Other Asset-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Amortized cost |  | 371 | 231
Gross unrealized gains |  | 2 | 3
Gross unrealized losses |  | (10) | (12)
Total available-for-sale, fair value |  | 363 | 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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