Investments (Schedule Of Amortized Cost And Fair Value Of HTM Fixed Maturities And Related OTTI Recognized In Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	$ 12,070	$ 12,581
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(45)	0
Debt securities, held to maturity, net carrying value	12,025
Held-to-maturity, Gross Unrealized Appreciation	487	427
Held-to-maturity, Gross Unrealized Depreciation	(41)	(3)
Held-to-maturity, Fair Value	12,471	13,005
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		0
U.S. Treasury and agency
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	1,208	1,318
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Debt securities, held to maturity, net carrying value	1,208
Held-to-maturity, Gross Unrealized Appreciation	75	29
Held-to-maturity, Gross Unrealized Depreciation	0	0
Held-to-maturity, Fair Value	1,283	1,347
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		0
Foreign
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	1,294	1,423
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(7)
Debt securities, held to maturity, net carrying value	1,287
Held-to-maturity, Gross Unrealized Appreciation	63	62
Held-to-maturity, Gross Unrealized Depreciation	(7)	0
Held-to-maturity, Fair Value	1,343	1,485
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		0
Corporate securities
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	2,272	2,349
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(36)
Debt securities, held to maturity, net carrying value	2,236
Held-to-maturity, Gross Unrealized Appreciation	113	121
Held-to-maturity, Gross Unrealized Depreciation	(27)	(2)
Held-to-maturity, Fair Value	2,322	2,468
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		0
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	2,266	2,331
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	2,265
Held-to-maturity, Gross Unrealized Appreciation	106	65
Held-to-maturity, Gross Unrealized Depreciation	(4)	0
Held-to-maturity, Fair Value	2,367	2,396
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		0
States, municipalities, and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	5,030	5,160
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	5,029
Held-to-maturity, Gross Unrealized Appreciation	130	150
Held-to-maturity, Gross Unrealized Depreciation	(3)	(1)
Held-to-maturity, Fair Value	$ 5,156	5,309
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities		$ 0

Debt securities, held to maturity, net carrying value

No definition available.

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- Definition

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as held-to-maturity that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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