Investment gains (losses) (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 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	$ 3,982	$ 31,317
Equity securities - Investment gains (losses) on securities sold during the period	(2,104)	370
Equity securities - Investment gains (losses), total	1,878	31,687
Fixed maturity securities - Gross realized gains	13	124
Fixed maturity securities - Gross realized losses	(12)	(52)
Other	(3)	2,999
Investment gains (losses)	$ 1,876	$ 34,758

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
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
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-Publisher FASB
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Amount of realized and unrealized gain (loss) on investment.

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Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

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

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