Investment gains (losses) (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Equity securities - Change in unrealized investment gains (losses) during the period on securities held at the end of the period	$ 18,643	$ (30,354)	$ 45,053	$ 33,267
Equity securities - Investment gains (losses) on securities sold during the period	1,868	605	1,221	1,748
Equity securities - Investment gains (losses), total	20,511	(29,749)	46,274	35,015
Fixed maturity securities - Gross realized gains	23	3	37	135
Fixed maturity securities - Gross realized losses	(17)	(29)	(57)	(106)
Other	(3)	(3)	(7)	2,997
Investment gains (losses)	$ 20,514	$ (29,778)	$ 46,247	$ 38,041

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).

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-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 of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of realized and unrealized gain (loss) on investment.

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