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.