Investments in fixed maturity securities - Amortized cost and estimated fair value of securities with fixed maturities (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Summary of Investment Holdings [Line Items]
Due in one year or less - amortized cost	$ 14,038
Due after one year through five years - amortized cost	7,426
Due after five years through ten years - amortized cost	780
Due after ten years - amortized cost	139
Amortized cost of mortgage-backed securities	182
Amortized cost of fixed maturity securities	22,565	$ 25,173
Due in one year or less - fair value	13,832
Due after one year through five years - fair value	7,370
Due after five years through ten years - fair value	1,016
Due after ten years - fair value	149
Fair value of mortgage-backed securities	199
Fair value of fixed maturity securities	$ 22,566	$ 25,128

Amortized cost of 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amortized cost of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27198-111563

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-Topic 320
-SubTopic 10
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Section 45
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