Investment and derivative contract gains/losses (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
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	$ (12,902)	$ 4,759	$ (80,496)	$ 36,163
Equity securities - Investment gains (losses) on securities sold during the period	(165)	75	(1,085)	889
Equity securities - Investment gains (losses), total	(13,067)	4,834	(81,581)	37,052
Fixed maturity securities - Gross realized gains	6	24	18	59
Fixed maturity securities - Gross realized losses	(433)	(7)	(509)	(20)
Other	(6)		(17)	144
Investment gains (losses)	(13,500)	4,851	(82,089)	37,235
Derivative contract gains (losses)	35	70	(273)	780
Investment and derivative contract gains (losses)	$ (13,465)	$ 4,921	$ (82,362)	$ 38,015

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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