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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, 2019 | Dec. 31, 2018
--- | --- | ---
Variable Interest Entity Primary Beneficiary [Member] |  |  |
Held To Maturity Securities [Abstract] |  |  |
Total held-to-maturity, amortized cost |  | $ 890 | $ 890
Gross unrealized gains |  | 87 | 35
Gross unrealized losses |  | 0 | 0
Total held-to-maturity investments, fair value |  | 977 | 925
Other-Than-Temporary Impairments | [1] | 0 | 0
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Held To Maturity Securities [Abstract] |  |  |
Total held-to-maturity, amortized cost |  | 890 | 890
Gross unrealized gains |  | 87 | 35
Gross unrealized losses |  | 0 | 0
Total held-to-maturity investments, fair value |  | 977 | 925
Other-Than-Temporary Impairments | [1] | 0 | 0
Fixed Maturities [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 3,008 | 3,817
Gross unrealized gains |  | 148 | 131
Gross unrealized losses |  | (43) | (167)
Total available-for-sale, fair value |  | 3,113 | 3,781
Other-than-temporary impairments | [1] | (33) | (26)
Fixed Maturities [Member] | U S Treasury And Government [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 807 | 1,093
Gross unrealized gains |  | 59 | 26
Gross unrealized losses |  | (1) | (10)
Total available-for-sale, fair value |  | 865 | 1,109
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | US States And Political Subdivisions [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 205 | 641
Gross unrealized gains |  | 24 | 97
Gross unrealized losses |  | 0 | (11)
Total available-for-sale, fair value |  | 229 | 727
Other-than-temporary impairments | [1] | 0 | 42
Fixed Maturities [Member] | Foreign Governments [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 8 | 9
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | 0 | 0
Total available-for-sale, fair value |  | 8 | 9
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Corporate Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 1,239 | 1,473
Gross unrealized gains |  | 58 | 6
Gross unrealized losses |  | (34) | (131)
Total available-for-sale, fair value |  | 1,263 | 1,348
Other-than-temporary impairments | [1] | (33) | (68)
Fixed Maturities [Member] | Residential Mortgage-Backed Agency [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 297 | 218
Gross unrealized gains |  | 4 | 1
Gross unrealized losses |  | (1) | (5)
Total available-for-sale, fair value |  | 300 | 214
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Residential Mortgage-Backed Non-Agency [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 25 | 30
Gross unrealized gains |  | 1 | 1
Gross unrealized losses |  | (5) | (4)
Total available-for-sale, fair value |  | 21 | 27
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 23 | 53
Gross unrealized gains |  | 1 | 0
Gross unrealized losses |  | 0 | (2)
Total available-for-sale, fair value |  | 24 | 51
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 129 | 122
Gross unrealized gains |  | 0 | 0
Gross unrealized losses |  | (2) | (3)
Total available-for-sale, fair value |  | 127 | 119
Other-than-temporary impairments | [1] | 0 | 0
Fixed Maturities [Member] | Other Asset-Backed [Member] |  |  |
Available For Sale Securities [Abstract] |  |  |
Total available-for-sale, amortized cost |  | 275 | 178
Gross unrealized gains |  | 1 | 0
Gross unrealized losses |  | 0 | (1)
Total available-for-sale, fair value |  | 276 | 177
Other-than-temporary impairments | [1] | $ 0 | $ 0
[1] | Represents unrealized gains or losses on OTTI 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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- Definition 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. + References No definition available. + Details
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