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Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - Fixed Maturities [Member] - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | $ 371 | $ 1,476
Less than 12 months, unrealized losses | (3) | (47)
12 months or longer, fair value | 206 | 944
12 months or longer, unrealized losses | (8) | (120)
Total available-for-sale, fair value | 577 | 2,420
Total available-for-sale, unrealized losses | (11) | (167)
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 148 | 231
Less than 12 months, unrealized losses | (1) | (1)
12 months or longer, fair value | 79 | 278
12 months or longer, unrealized losses | (1) | (9)
Total available-for-sale, fair value | 227 | 509
Total available-for-sale, unrealized losses | (2) | (10)
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 11 | 60
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 15 | 135
12 months or longer, unrealized losses | 0 | (10)
Total available-for-sale, fair value | 26 | 195
Total available-for-sale, unrealized losses | 0 | (11)
Foreign Government Debt [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value |  | 5
Less than 12 months, unrealized losses |  | 0
12 months or longer, fair value |  | 2
12 months or longer, unrealized losses |  | 0
Total available-for-sale, fair value |  | 7
Total available-for-sale, unrealized losses |  | 0
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 53 | 900
Less than 12 months, unrealized losses | (1) | (41)
12 months or longer, fair value | 10 | 335
12 months or longer, unrealized losses | 0 | (90)
Total available-for-sale, fair value | 63 | 1,235
Total available-for-sale, unrealized losses | (1) | (131)
Residential Mortgage Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 62 | 29
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 7 | 118
12 months or longer, unrealized losses | 0 | (4)
Total available-for-sale, fair value | 69 | 147
Total available-for-sale, unrealized losses | 0 | (5)
Residential Mortgage Backed Non Agency [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 | 11 | 13
12 months or longer, unrealized losses | (5) | (4)
Total available-for-sale, fair value | 11 | 15
Total available-for-sale, unrealized losses | (5) | (4)
Commercial Mortgage Backed Securities [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 5 | 24
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 0 | 21
12 months or longer, unrealized losses | 0 | (2)
Total available-for-sale, fair value | 5 | 45
Total available-for-sale, unrealized losses | 0 | (2)
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 44 | 98
Less than 12 months, unrealized losses | 0 | (3)
12 months or longer, fair value | 77 | 7
12 months or longer, unrealized losses | (2) | 0
Total available-for-sale, fair value | 121 | 105
Total available-for-sale, unrealized losses | (2) | (3)
Other Asset Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 48 | 127
Less than 12 months, unrealized losses | (1) | 0
12 months or longer, fair value | 7 | 35
12 months or longer, unrealized losses | 0 | (1)
Total available-for-sale, fair value | 55 | 162
Total available-for-sale, unrealized losses | $ (1) | $ (1)

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- Definition 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 No definition available. + Details
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- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
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