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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - Fixed Maturities [Member] - USD ($) $ in Millions | Mar. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | $ 3,128 | $ 2,316
Allowance for Credit Losess | (3) | 0
Gross unrealized gains | 62 | 150
Gross unrealized losses | (93) | (9)
Total available-for-sale, fair value | 3,094 | 2,457
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 862 | 782
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 28 | 54
Gross unrealized losses | (15) | (2)
Total available-for-sale, fair value | 875 | 834
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 606 | 140
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 13 | 27
Gross unrealized losses | (20) | 0
Total available-for-sale, fair value | 599 | 167
Foreign Governments [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 23 | 13
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 1
Gross unrealized losses | (1) | 0
Total available-for-sale, fair value | 22 | 14
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 1,013 | 905
Allowance for Credit Losess | (3) | 0
Gross unrealized gains | 13 | 53
Gross unrealized losses | (44) | (5)
Total available-for-sale, fair value | 979 | 953
Residential Mortgage-Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 186 | 190
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 3
Gross unrealized losses | (8) | (1)
Total available-for-sale, fair value | 178 | 192
Residential Mortgage-Backed Non-Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 124 | 80
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 8 | 12
Gross unrealized losses | (1) | 0
Total available-for-sale, fair value | 131 | 92
Commercial Mortgage-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 10 | 10
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (1) | 0
Total available-for-sale, fair value | 9 | 10
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 125 | 101
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (1) | 0
Total available-for-sale, fair value | 124 | 101
Other Asset-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 179 | 95
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (2) | (1)
Total available-for-sale, fair value | $ 177 | $ 94

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