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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, 2020 | Dec. 31, 2019
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | $ 325 | $ 371
Less than 12 months, unrealized losses | (3) | (3)
12 months or longer, fair value | 91 | 206
12 months or longer, unrealized losses | (2) | (8)
Total available-for-sale, fair value | 416 | 577
Total available-for-sale, unrealized losses | (5) | (11)
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 99 | 148
Less than 12 months, unrealized losses | (1) | (1)
12 months or longer, fair value | 0 | 79
12 months or longer, unrealized losses | 0 | (1)
Total available-for-sale, fair value | 99 | 227
Total available-for-sale, unrealized losses | (1) | (2)
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value |  | 11
Less than 12 months, unrealized losses |  | 0
12 months or longer, fair value |  | 15
12 months or longer, unrealized losses |  | 0
Total available-for-sale, fair value |  | 26
Total available-for-sale, unrealized losses |  | 0
Foreign Government Debt [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 2 |
Less than 12 months, unrealized losses | 0 |
12 months or longer, fair value | 0 |
12 months or longer, unrealized losses | 0 |
Total available-for-sale, fair value | 2 |
Total available-for-sale, unrealized losses | 0 |
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 103 | 53
Less than 12 months, unrealized losses | (1) | (1)
12 months or longer, fair value | 7 | 10
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 110 | 63
Total available-for-sale, unrealized losses | (1) | (1)
Residential Mortgage Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 53 | 62
Less than 12 months, unrealized losses | (1) | 0
12 months or longer, fair value | 0 | 7
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 53 | 69
Total available-for-sale, unrealized losses | (1) | 0
Residential Mortgage Backed Non Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 2 | 0
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 1 | 11
12 months or longer, unrealized losses | 0 | (5)
Total available-for-sale, fair value | 3 | 11
Total available-for-sale, unrealized losses | 0 | (5)
Commercial Mortgage Backed Securities [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 0 | 5
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 5 | 0
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 5 | 5
Total available-for-sale, unrealized losses | 0 | 0
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 37 | 44
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 78 | 77
12 months or longer, unrealized losses | (2) | (2)
Total available-for-sale, fair value | 115 | 121
Total available-for-sale, unrealized losses | (2) | (2)
Other Asset Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 29 | 48
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 0 | 7
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 29 | 55
Total available-for-sale, unrealized losses | $ 0 | $ (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=121645371&loc=d3e27337-111563 + Details
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