Derivatives - Credit Risk Assumed through Credit Derivatives (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2025	Dec. 31, 2024
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 6,757	$ 7,081
Fair Value	31	45
Credit derivatives
Credit Derivatives [Line Items]
Derivative, Notional Amount	493	493
Fair Value	22	29
Derivative, Nominal Value, Amount Offset Against Collateral, Net	493	493
Offsetting Fair Value	(22)	(29)
Standard & Poor's, AAA Rating [Member] \| Basket credit default swaps \| Credit derivatives \| Investment grade risk exposure
Credit Derivatives [Line Items]
Derivative, Notional Amount	100	100
Fair Value	$ 0	$ 0
Weighted Average Years to Maturity	3 years	4 years
Derivative, Nominal Value, Amount Offset Against Collateral, Net	$ 100	$ 100
Offsetting Fair Value	0	0
Standard & Poor's, B+ Rating \| Basket credit default swaps \| Credit derivatives \| Below investment grade risk exposure
Credit Derivatives [Line Items]
Derivative, Notional Amount	392	392
Fair Value	$ 23	$ 30
Weighted Average Years to Maturity	3 years	3 years
Derivative, Nominal Value, Amount Offset Against Collateral, Net	$ 392	$ 392
Offsetting Fair Value	(23)	(30)
Standard & Poor's, CCC Rating \| Basket credit default swaps \| Credit derivatives \| Below investment grade risk exposure
Credit Derivatives [Line Items]
Derivative, Notional Amount	1	1
Fair Value	$ (1)	$ (1)
Average Term of Credit Risk Derivatives Less than 1 Year	Less than 1 year	Less than 1 year
Derivative, Nominal Value, Amount Offset Against Collateral, Net	$ 1	$ 1
Offsetting Fair Value	$ 1	$ 1

Average Term of Credit Risk Derivatives Less than 1 Year

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- Definition

Derivative, Nominal Value, Amount Offset Against Collateral, Net

+ References

No definition available.

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- Definition

Average period covered by credit risk derivative contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(1)
-SubTopic 10
-Topic 815
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

The net amount as of the balance sheet date of the fair value of derivative assets and derivative liabilities that in accordance with the entity's accounting policy were offset against collateral under a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

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