Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	$ 562	$ 541
Allowance for Credit Losess	0	0
Gross unrealized gains	8	5
Gross unrealized losses	(27)	(38)
Total available-for-sale, fair value	543	508
US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	136	173
Allowance for Credit Losess	0	0
Gross unrealized gains	3	2
Gross unrealized losses	(8)	(11)
Total available-for-sale, fair value	131	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	(2)	(3)
Total available-for-sale, fair value	24	20
Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	1,007	862
Allowance for Credit Losess	0	0
Gross unrealized gains	3	1
Gross unrealized losses	(129)	(148)
Total available-for-sale, fair value	881	715
Residential Mortgage-Backed Agency [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	237	217
Allowance for Credit Losess	0	0
Gross unrealized gains	1	0
Gross unrealized losses	(20)	(22)
Total available-for-sale, fair value	218	195
Residential Mortgage-Backed Non-Agency [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	104	96
Allowance for Credit Losess	0	0
Gross unrealized gains	2	3
Gross unrealized losses	(10)	(11)
Total available-for-sale, fair value	96	88
Commercial Mortgage-Backed [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	27	24
Allowance for Credit Losess	0	0
Gross unrealized gains	0	0
Gross unrealized losses	(1)	(1)
Total available-for-sale, fair value	26	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	(4)	(5)
Total available-for-sale, fair value	111	112
Other Asset-Backed [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	88	110
Allowance for Credit Losess	0	0
Gross unrealized gains	1	0
Gross unrealized losses	(3)	(4)
Total available-for-sale, fair value	86	106
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Total available-for-sale, amortized cost	2,300	2,163
Allowance for Credit Losess	0	0
Gross unrealized gains	20	11
Gross unrealized losses	(204)	(243)
Total available-for-sale, fair value	$ 2,116	$ 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).

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-Publisher FASB
-Name Accounting Standards Codification
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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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Reference 1: 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).

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