Investments - Schedule of changes in unrealized appreciation (depreciation) of available for sale securities and other investments (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	$ (17,904)	$ 5,846	$ (38,071)	$ (5,803)
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	(101)	530	347	1,022
Less: Net losses recognized during the period on equity securities and other investments sold during the period	(34)	(188)	57	(185)
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	(67)	718	290	1,207
Fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	(17,897)	5,851	(38,057)	(5,798)
Other investments
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	(7)	(5)	(14)	(5)
Equity securities
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	(30)	(13)	(57)	9
Less: Net losses recognized during the period on equity securities and other investments sold during the period	(1)	(179)	93	(200)
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	(29)	166	(150)	209
Other invested assets
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	(71)	543	404	1,013
Less: Net losses recognized during the period on equity securities and other investments sold during the period	(33)	(9)	(36)	15
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	$ (38)	$ 552	$ 440	$ 998

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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117546-209714

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117546-209714

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Amount, before tax and adjustment, of unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27357-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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