Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment [Line Items]
Gross realized gains on securities	$ 1	$ 36	$ 14
Gross realized losses on securities	(4)	(18)	(2)
Foreign exchange (losses) gains	(3)	11	(7)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(3)	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery	(12)	0	0
Net realized (losses) gains	(22)	31	7
Gain (Loss) on Investments [Member]
Investment [Line Items]
Foreign exchange (losses) gains	$ (4)	$ 14	$ (5)

Amount of expense (reversal of expense) for 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), not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis, with previously recorded allowance.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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-Paragraph 9
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Amount of decrease in 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) from intent to sell or more likely than not will be required to sell before recovery of amortized cost basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of realized gain 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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Amount of realized 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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Amount, before tax, of realized and unrealized gain (loss) from foreign currency transaction.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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