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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | $ 462 | $ 541
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 1 | 5
Gross unrealized losses | (41) | (38)
Total available-for-sale, fair value | 422 | 508
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 131 | 173
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 1 | 2
Gross unrealized losses | (15) | (11)
Total available-for-sale, fair value | 117 | 164
Foreign Governments [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 25 | 23
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 1 | 0
Gross unrealized losses | (4) | (3)
Total available-for-sale, fair value | 22 | 20
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 884 | 862
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 1
Gross unrealized losses | (158) | (148)
Total available-for-sale, fair value | 726 | 715
Residential Mortgage-Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 197 | 217
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (26) | (22)
Total available-for-sale, fair value | 171 | 195
Residential Mortgage-Backed Non-Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 33 | 96
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 3
Gross unrealized losses | (7) | (11)
Total available-for-sale, fair value | 26 | 88
Commercial Mortgage-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 22 | 24
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (1) | (1)
Total available-for-sale, fair value | 21 | 23
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 114 | 117
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 1 | 0
Gross unrealized losses | (2) | (5)
Total available-for-sale, fair value | 113 | 112
Other Asset-Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 46 | 110
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 0 | 0
Gross unrealized losses | (3) | (4)
Total available-for-sale, fair value | 43 | 106
Fixed Maturities [Member] |  |
Available For Sale Securities [Abstract] |  |
Total available-for-sale, amortized cost | 1,914 | 2,163
Allowance for Credit Losess | 0 | 0
Gross unrealized gains | 4 | 11
Gross unrealized losses | (257) | (243)
Total available-for-sale, fair value | $ 1,661 | $ 1,931

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-2 + Details
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