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

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).

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

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
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