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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 | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | $ 646 | $ 325
Less than 12 months, unrealized losses | (26) | (3)
12 months or longer, fair value | 88 | 91
12 months or longer, unrealized losses | (2) | (2)
Total available-for-sale, fair value | 734 | 416
Total available-for-sale, unrealized losses | (28) | (5)
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 125 | 99
Less than 12 months, unrealized losses | (5) | (1)
12 months or longer, fair value | 0 | 0
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 125 | 99
Total available-for-sale, unrealized losses | (5) | (1)
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 4 |
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 | 4 |
Total available-for-sale, unrealized losses | 0 |
Foreign Government Debt [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 6 | 2
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 0 | 0
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 6 | 2
Total available-for-sale, unrealized losses | 0 | 0
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 278 | 103
Less than 12 months, unrealized losses | (15) | (1)
12 months or longer, fair value | 15 | 7
12 months or longer, unrealized losses | (1) | 0
Total available-for-sale, fair value | 293 | 110
Total available-for-sale, unrealized losses | (16) | (1)
Residential Mortgage Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 100 | 53
Less than 12 months, unrealized losses | (3) | (1)
12 months or longer, fair value | 0 | 0
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 100 | 53
Total available-for-sale, unrealized losses | (3) | (1)
Residential Mortgage Backed Non Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 35 | 2
Less than 12 months, unrealized losses | (3) | 0
12 months or longer, fair value | 1 | 1
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 36 | 3
Total available-for-sale, unrealized losses | (3) | 0
Commercial Mortgage Backed Securities [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 | 0 | 5
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 2 | 5
Total available-for-sale, unrealized losses | 0 | 0
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 19 | 37
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 71 | 78
12 months or longer, unrealized losses | (1) | (2)
Total available-for-sale, fair value | 90 | 115
Total available-for-sale, unrealized losses | (1) | (2)
Other Asset Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 77 | 29
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 1 | 0
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 78 | 29
Total available-for-sale, unrealized losses | $ 0 | $ 0

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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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