Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Schedule of Available for Sale Securities
Amortized cost, net	$ 45,370	$ 41,376
Gross unrealized gains	92	1,002
Gross unrealized losses	(2,977)	(242)
Fixed income securities	42,485	42,136
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	8,123	6,287
Gross unrealized gains	6	12
Gross unrealized losses	(231)	(26)
Fixed income securities	7,898	6,273
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	6,500	6,130
Gross unrealized gains	36	279
Gross unrealized losses	(326)	(16)
Fixed income securities	6,210	6,393
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	28,562	26,834
Gross unrealized gains	46	688
Gross unrealized losses	(2,345)	(192)
Fixed income securities	26,263	27,330
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	997	982
Gross unrealized gains	0	9
Gross unrealized losses	(40)	(6)
Fixed income securities	957	985
ABS
Schedule of Available for Sale Securities
Amortized cost, net	1,188	1,143
Gross unrealized gains	4	14
Gross unrealized losses	(35)	(2)
Fixed income securities	$ 1,157	$ 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 https://asc.fasb.org/extlink&oid=126970911&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).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126970911&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 https://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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