Investments - Roll Forward of Credit Losses in the Investment Portfolio (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Roll Forward of Credit Losses in the Investment Portfolio
Balance, beginning of period	$ 51	$ 39	$ 42	$ 78
Additions on securities for which credit impairments were not previously recognized	1	0	4	1
Additions from purchases of securities accounted for as purchased financial assets with credit deterioration	2	0	2	0
Additions (reductions) on securities for which credit impairments were previously recognized	3	(4)	9	(2)
Reductions for securities sold and other settlements	0	0	0	(42)
Balance, end of period	$ 57	$ 35	$ 57	$ 35

Amount of increase in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and beneficial interest, purchased with credit deterioration.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Amount excluding accrued interest, of allowance for credit loss 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://www.xbrl.org/2003/role/disclosureRef
-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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Data Type:	xbrli:monetaryItemType
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- Definition

Amount, excluding accrued interest, of credit loss expense on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) with no credit loss previously recorded.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) with previously recorded allowance and not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

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