Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Schedule of Available for Sale Securities
Amortized cost, net	$ 46,120	$ 45,370
Gross unrealized, Gains	211	92
Gross unrealized, Losses	(2,228)	(2,977)
Fixed income securities	44,103	42,485
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	7,826	8,123
Gross unrealized, Gains	21	6
Gross unrealized, Losses	(152)	(231)
Fixed income securities	7,695	7,898
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	6,499	6,500
Gross unrealized, Gains	65	36
Gross unrealized, Losses	(240)	(326)
Fixed income securities	6,324	6,210
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	29,705	28,562
Gross unrealized, Gains	118	46
Gross unrealized, Losses	(1,787)	(2,345)
Fixed income securities	28,036	26,263
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	1,112	997
Gross unrealized, Gains	3	0
Gross unrealized, Losses	(24)	(40)
Fixed income securities	1,091	957
ABS
Schedule of Available for Sale Securities
Amortized cost, net	978	1,188
Gross unrealized, Gains	4	4
Gross unrealized, Losses	(25)	(35)
Fixed income securities	$ 957	$ 1,157

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).

+ References

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 (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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