Investments - Schedule of Securities Pledged by Contractual Maturity (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 283	$ 205
Total gross secured borrowings	283	205
Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	276	202
Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	1
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	6	3
Overnight and Continuous
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	283	205
Overnight and Continuous \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	276	202
Overnight and Continuous \| Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	1
Overnight and Continuous \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	6	3
Up to 30 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
Up to 30 Days \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Up to 30 Days \| Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0
Up to 30 Days \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
30-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
30-90 Days \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
30-90 Days \| Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0
30-90 Days \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Greater Than 90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Total gross secured borrowings	0	0
Greater Than 90 Days \| Corporate bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0	0
Greater Than 90 Days \| Foreign government bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	0
Greater Than 90 Days \| Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities pledged under securities lending agreements	$ 0	$ 0

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial assets at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-7

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-7

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

+ References

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-7

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