Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available for Sale Securities
Amortized cost, net	$ 42,027	$ 41,376
Gross unrealized, Gains	189	1,002
Gross unrealized, Losses	(1,471)	(242)
Fixed income securities, at fair value	40,745	42,136
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	6,613	6,287
Gross unrealized, Gains	3	12
Gross unrealized, Losses	(131)	(26)
Fixed income securities, at fair value	6,485	6,273
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	5,805	6,130
Gross unrealized, Gains	54	279
Gross unrealized, Losses	(161)	(16)
Fixed income securities, at fair value	5,698	6,393
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	26,334	26,834
Gross unrealized, Gains	120	688
Gross unrealized, Losses	(1,118)	(192)
Fixed income securities, at fair value	25,336	27,330
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	1,092	982
Gross unrealized, Gains	1	9
Gross unrealized, Losses	(40)	(6)
Fixed income securities, at fair value	1,053	985
ABS
Schedule of Available for Sale Securities
Amortized cost, net	2,183	1,143
Gross unrealized, Gains	11	14
Gross unrealized, Losses	(21)	(2)
Fixed income securities, at fair value	$ 2,173	$ 1,155

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

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Amortized cost excluding accrued interest, after allowance for credit loss, 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amount excluding accrued interest, of 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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