Investment gains (losses) (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 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	$ 17,252	$ 33,046	$ 29,711	$ 63,763
Equity securities - Investment gains (losses) on securities sold during the period	6,633	31	(3,948)	1,001
Equity securities - Investment gains (losses), total	23,885	33,077	25,763	64,764
Fixed maturity securities - Gross realized gains	1	8	14	132
Fixed maturity securities - Gross realized losses	(28)	(25)	(40)	(77)
Other	(1)	1	(4)	3,000
Investment gains (losses)	$ 23,857	$ 33,061	$ 25,733	$ 67,819

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
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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