Investment gains (losses) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Equity securities - Change in unrealized investment gains (losses) during the year on securities held at the end of the year	$ 49,297	$ 69,144	$ (63,120)
Equity securities - Investment gains (losses) during the year on securities sold	3,523	2,698	(3,927)
Equity securities - Investment gains (losses), total	52,820	71,842	(67,047)
Fixed maturity securities - Gross realized gains	28	139	134
Fixed maturity securities - Gross realized losses	(71)	(86)	(684)
Other	22	2,960	(302)
Investment gains (losses)	$ 52,799	$ 74,855	$ (67,899)

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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