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Debt (Long-Term Debt) (Detail) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2023 | Jun. 30, 2023 | Dec. 31, 2022
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross |  | $ 2,585 |  | $ 2,428
Debt issuance costs |  | 7 |  | 8
7.000% Debentures Due 2025 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross |  | $ 45 |  | 45
Long-term debt, interest rate |  | 7.00% |  |
Long-term debt, maturity year |  | 2025 |  |
7.150% Debentures Due 2027 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross |  | $ 96 |  | 96
Long-term debt, interest rate |  | 7.15% |  |
Long-term debt, maturity year |  | 2027 |  |
6.625% Debentures Due 2028 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross |  | $ 112 |  | 112
Long-term debt, interest rate |  | 6.625% |  |
Long-term debt, maturity year |  | 2028 |  |
5.700% Senior Notes Due 2034 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross | [1] | $ 21 |  | 21
Long-term debt, interest rate |  | 5.70% |  |
Long-term debt, maturity year |  | 2034 |  |
Surplus Notes due 2033 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Surplus Notes | [2] | $ 940 |  | 940
Long-term debt, interest rate |  |  | 11.26% |
Long-term debt, maturity year |  | 2033 |  |
Surplus Notes due 2033 [Member] | Secured Overnight Financing Rate ("SOFR") [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, interest rate |  | 11.52161% |  |
Accrued Interest [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt, gross |  | $ 1,378 |  | $ 1,222
[1] | Callable anytime at the greater of par or the present value of the remaining scheduled payments of principal and interest.
[2] | Contractual interest rate is based on three month LIBOR plus 11.26% until June 30, 2023. In connection with the Company's transition from LIBOR, effective July 1, 2023, the interest rate is based on three-month term Secured Overnight Financing Rate ("SOFR") plus 11.52161% at each future reset date.

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