Investments in fixed maturity securities (Detail) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	$ 17,461	$ 17,525
Unrealized gains on fixed maturity securities	269	304
Unrealized losses on fixed maturity securities	(61)	(13)
Fair value of fixed maturity securities	17,669	17,816
U.S. Treasury, U.S. government corporations and agencies [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	3,880	3,835
Unrealized gains on fixed maturity securities	5	14
Unrealized losses on fixed maturity securities	(5)
Fair value of fixed maturity securities	3,880	3,849
Foreign governments [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	12,391	12,493
Unrealized gains on fixed maturity securities	51	58
Unrealized losses on fixed maturity securities	(51)	(9)
Fair value of fixed maturity securities	12,391	12,542
Corporate and Other [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	1,190	1,197
Unrealized gains on fixed maturity securities	213	232
Unrealized losses on fixed maturity securities	(5)	(4)
Fair value of fixed maturity securities	$ 1,398	$ 1,425

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