Fair Value - Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Corporate bonds and other
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	$ 810	$ 937
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income		(1)
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Included in OCI	38	(184)
Purchases	219	137
Sales		(5)
Settlements	(33)	(84)
Transfers into Level 3	11	10
Transfers out of Level 3
Balance at end of period	1,045	810
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	38	(183)
States, municipalities and political subdivisions
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	43	56
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Included in OCI	1	(13)
Purchases
Sales
Settlements
Transfers into Level 3
Transfers out of Level 3
Balance at end of period	44	43
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	1	(13)
Asset-backed
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	788	556
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	16	25
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Included in OCI	9	(126)
Purchases	248	424
Sales		(2)
Settlements	(64)	(70)
Transfers into Level 3	23	75
Transfers out of Level 3	(119)	(94)
Balance at end of period	901	788
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	9	(125)
Fixed maturities available-for-sale
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	1,641	1,549
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	16	24
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Included in OCI	48	(323)
Purchases	467	561
Sales	0	(7)
Settlements	(97)	(154)
Transfers into Level 3	34	85
Transfers out of Level 3	(119)	(94)
Balance at end of period	1,990	1,641
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31	0	0
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31	48	(321)
Equity securities
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	35	29
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	(7)	(9)
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Included in OCI
Purchases		19
Sales	(4)	(3)
Settlements		9
Transfers into Level 3
Transfers out of Level 3		(10)
Balance at end of period	24	35
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at December 31	(7)	(4)
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at December 31

Amount of unrealized gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Name Accounting Standards Codification
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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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