Investment and derivative contract gains/losses (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 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	$ (1,775)	$ 4,630
Equity securities - Investment gains (losses) on securities sold during the period	89	430
Equity securities - Investment gains (losses), total	(1,686)	5,060
Fixed maturity securities - Gross realized gains	6	20
Fixed maturity securities - Gross realized losses	(49)	(1)
Other	(6)	132
Investment gains (losses)	(1,735)	5,211
Derivative contract gains (losses)	(243)	489
Investment and derivative contract gains (losses)	$ (1,978)	$ 5,700

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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