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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions	Mar. 31, 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	$ 1,467	$ 1,391
Allowance for Credit Losess	0	0
Gross unrealized gains	5	5
Gross unrealized losses	(139)	(160)
Total available-for-sale, fair value	1,333	1,236
U.S. Treasury And Government Agency [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	508	500
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(13)	(19)
Total available-for-sale, fair value	495	481
US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	109	110
Allowance for Credit Losess	0	0
Gross unrealized gains	2	2
Gross unrealized losses	(9)	(11)
Total available-for-sale, fair value	102	101
Foreign Governments [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	9	12
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(2)	(2)
Total available-for-sale, fair value	7	10
Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	485	496
Allowance for Credit Losess	0	0
Gross unrealized gains	1	1
Gross unrealized losses	(98)	(106)
Total available-for-sale, fair value	388	391
Residential Mortgage-Backed Agency [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	123	127
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(14)	(16)
Total available-for-sale, fair value	109	111
Residential Mortgage-Backed Non-Agency [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	13	36
Allowance for Credit Losess	0	0
Gross unrealized gains	0	1
Gross unrealized losses	(1)	(5)
Total available-for-sale, fair value	12	32
Commercial Mortgage-Backed [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	15	7
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Total available-for-sale, fair value	15	7
Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	58	71
Allowance for Credit Losess	0	0
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Total available-for-sale, fair value	59	72
Other Asset-Backed [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	147	32
Allowance for Credit Losess	0	0
Gross unrealized gains	1	0
Gross unrealized losses	(2)	(1)
Total available-for-sale, fair value	$ 146	$ 31

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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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