Investments - Amortized cost, gross unrealized gains and losses and fair value for fixed income securities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available for Sale Securities
Amortized cost, net	$ 41,376	$ 40,034
Gross unrealized gains	1,002	2,563
Gross unrealized losses	(242)	(32)
Fixed income securities	42,136	42,565
U.S. government and agencies
Schedule of Available for Sale Securities
Amortized cost, net	6,287	2,058
Gross unrealized gains	12	50
Gross unrealized losses	(26)	(1)
Fixed income securities	6,273	2,107
Municipal
Schedule of Available for Sale Securities
Amortized cost, net	6,130	7,100
Gross unrealized gains	279	480
Gross unrealized losses	(16)	(2)
Fixed income securities	6,393	7,578
Corporate
Schedule of Available for Sale Securities
Amortized cost, net	26,834	29,057
Gross unrealized gains	688	1,986
Gross unrealized losses	(192)	(26)
Fixed income securities	27,330	31,017
Foreign government
Schedule of Available for Sale Securities
Amortized cost, net	982	921
Gross unrealized gains	9	37
Gross unrealized losses	(6)	0
Fixed income securities	985	958
ABS
Schedule of Available for Sale Securities
Amortized cost, net	1,143	898
Gross unrealized gains	14	10
Gross unrealized losses	(2)	(3)
Fixed income securities	$ 1,155	$ 905

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).

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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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