Fair Value - Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Corporate bonds and other
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	$ 1,594	$ 1,388	$ 1,483	$ 1,278
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	(2)		(5)	1
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	(80)	21	(102)	58
Purchases	61	24	225	123
Sales
Settlements	(6)	(33)	(34)	(75)
Transfers into Level 3				15
Transfers out of Level 3	(7)		(7)
Balance at ending of period	1,560	1,400	1,560	1,400
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at September 30
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at September 30	(80)	21	(102)	55
States, municipalities and political subdivisions
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	44	44	45	42
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 OCI	(2)		(3)	2
Purchases
Sales
Settlements	(1)		(1)
Transfers into Level 3
Transfers out of Level 3
Balance at ending of period	41	44	41	44
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at September 30
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at September 30	(2)		(3)	2
Asset-backed
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	943	886	998	876
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	4	8	8	13
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	(35)	8	(56)	5
Purchases	57	93	139	142
Sales
Settlements	(30)	(36)	(76)	(77)
Transfers into Level 3
Transfers out of Level 3	(13)		(87)
Balance at ending of period	926	959	926	959
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at September 30
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at September 30	(35)	9	(56)	6
Fixed maturities available-for-sale
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	2,581	2,318	2,526	2,196
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	2	8	3	14
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI	(117)	29	(161)	65
Purchases	118	117	364	265
Sales	0	0	0	0
Settlements	(37)	(69)	(111)	(152)
Transfers into Level 3	0	0	0	15
Transfers out of Level 3	(20)	0	(94)	0
Balance at ending of period	2,527	2,403	2,527	2,403
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at September 30	0	0	0	0
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at September 30	(117)	30	(161)	63
Equity securities
Reconciliations for All Assets and Liabilities [Roll Forward]
Balance at beginning of period	30	10	33	20
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income	1		3	1
Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI
Purchases
Sales			(5)	(7)
Settlements				(4)
Transfers into Level 3
Transfers out of Level 3
Balance at ending of period	31	10	31	10
Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at September 30	1			(1)
Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at September 30

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.

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

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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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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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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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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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