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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 | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | $ 2,335 | $ 2,360
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 146 | 184
Gross unrealized losses | (8) | (5)
Total available-for-sale, fair value | 2,473 | 2,539
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 739 | 775
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 58 | 75
Gross unrealized losses | (1) | (1)
Total available-for-sale, fair value | 796 | 849
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 156 | 162
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 29 | 32
Gross unrealized losses | 0 | 0
Total available-for-sale, fair value | 185 | 194
Foreign Governments [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 16 | 11
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 1 | 1
Gross unrealized losses | 0 | 0
Total available-for-sale, fair value | 17 | 12
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 864 | 827
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 43 | 64
Gross unrealized losses | (5) | (1)
Total available-for-sale, fair value | 902 | 890
Residential Mortgage-Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 219 | 305
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 5 | 8
Gross unrealized losses | (1) | (1)
Total available-for-sale, fair value | 223 | 312
Residential Mortgage-Backed Non-Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 85 | 22
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 10 | 3
Gross unrealized losses | 0 | 0
Total available-for-sale, fair value | 95 | 25
Commercial Mortgage-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 12 | 17
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 1
Gross unrealized losses | 0 | 0
Total available-for-sale, fair value | 12 | 18
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 118 | 120
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (1) | (2)
Total available-for-sale, fair value | 117 | 118
Other Asset-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 126 | 121
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | 0 | 0
Total available-for-sale, fair value | $ 126 | $ 121

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