Investments in fixed maturity securities (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	$ 14,776	$ 15,214
Unrealized gains on fixed maturity securities	336	257
Unrealized losses on fixed maturity securities	(28)	(107)
Fair value of fixed maturity securities	15,084	15,364
U.S. Treasury, U.S. government corporations and agencies [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	3,845	4,447
Unrealized gains on fixed maturity securities	13	16
Unrealized losses on fixed maturity securities	(1)	(4)
Fair value of fixed maturity securities	3,857	4,459
Foreign governments [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	9,674	9,443
Unrealized gains on fixed maturity securities	86	16
Unrealized losses on fixed maturity securities	(24)	(97)
Fair value of fixed maturity securities	9,736	9,362
Corporate and Other [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	1,257	1,324
Unrealized gains on fixed maturity securities	237	225
Unrealized losses on fixed maturity securities	(3)	(6)
Fair value of fixed maturity securities	$ 1,491	$ 1,543

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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+ Details

- Definition

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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+ Details