Investment and derivative contract gains (losses) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
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	$ 69,144	$ (63,120)	$ 76,375
Equity securities - Investment gains (losses) during the year on securities sold	2,698	(3,927)	997
Equity securities - Investment gains (losses), total	71,842	(67,047)	77,372
Fixed maturity securities - Gross realized gains	139	134	85
Fixed maturity securities - Gross realized losses	(86)	(684)	(29)
Other	2,960	(26)	148
Investment gains (losses)	74,855	(67,623)	77,576
Derivative contract gains (losses)		(276)	966
Investment and derivative contract gains (losses)	$ 74,855	$ (67,899)	$ 78,542

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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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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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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

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Amount of gain (loss) included in earnings for investments classified as other.

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The aggregate amount of gains or losses resulting from nonoperating activities (for example, interest and dividend revenue, property, plant and equipment impairment loss, and so forth).

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