Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Available For Sale Securities [Abstract]
Investment, Type [Extensible Enumeration]	Fixed Maturities [Member]	Fixed Maturities [Member]
Total available-for-sale, amortized cost	$ 1,521	$ 1,391
Allowance for Credit Losess	0	0
Gross unrealized gains	7	5
Gross unrealized losses	(127)	(160)
Total available-for-sale, fair value	1,401	1,236
U.S. Treasury And Government Agency [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	570	500
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(10)	(19)
Total available-for-sale, fair value	560	481
US States And Political Subdivisions [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	102	110
Allowance for Credit Losess	0	0
Gross unrealized gains	3	2
Gross unrealized losses	(8)	(11)
Total available-for-sale, fair value	97	101
Foreign Governments [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	7	12
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(2)	(2)
Total available-for-sale, fair value	5	10
Corporate Obligations [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	445	496
Allowance for Credit Losess	0	0
Gross unrealized gains	1	1
Gross unrealized losses	(94)	(106)
Total available-for-sale, fair value	352	391
Residential Mortgage-Backed Agency [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	120	127
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(12)	(16)
Total available-for-sale, fair value	108	111
Residential Mortgage-Backed Non-Agency [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	12	36
Allowance for Credit Losess	0	0
Gross unrealized gains	0	1
Gross unrealized losses	0	(5)
Total available-for-sale, fair value	12	32
Commercial Mortgage-Backed [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	12	7
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Total available-for-sale, fair value	12	7
Collateralized Debt Obligations [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	25	71
Allowance for Credit Losess	0	0
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Total available-for-sale, fair value	26	72
Other Asset-Backed [Member] \| Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	228	32
Allowance for Credit Losess	0	0
Gross unrealized gains	2	0
Gross unrealized losses	(1)	(1)
Total available-for-sale, fair value	$ 229	$ 31

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).

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Amount, before tax, of unrealized loss 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).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Indicates type of investment. Includes, but is not limited to, common stock, preferred stock, convertible security, fixed income security, government security, option purchased, warrant, loan participation and assignment, commercial paper, bankers' acceptance, certificates of deposit, short-term security, repurchase agreement, and other investment company.

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