Fair Value Measurements - Fair Value Recurring Basis, Unobservable Input (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Liabilities
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses)	Net realized gains (losses)
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets
Beginning balance	$ 2,992	$ 2,487
Total realized/unrealized gains (losses), Included in net income	(4)	3
Total realized/unrealized gains (losses), Included in OCI	19	(5)
Purchases	454	291
Settlements	(151)	(49)
Sales	(11)	(2)
Transfers into Level 3	73	6
Transfers out of Level 3	(148)	(47)
Ending balance	3,224	2,684
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Equity securities, at fair value
Assets
Beginning balance	87	58
Total realized/unrealized gains (losses), Included in net income	(1)	0
Total realized/unrealized gains (losses), Included in OCI	0	0
Purchases	8	0
Settlements	(3)	0
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	91	58
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Short-term investments
Assets
Beginning balance	98	25
Total realized/unrealized gains (losses), Included in net income	0	0
Total realized/unrealized gains (losses), Included in OCI	0	0
Purchases	10	1
Settlements	(49)	0
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	59	26
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	2,610	2,237
Total realized/unrealized gains (losses), Included in net income	1	0
Total realized/unrealized gains (losses), Included in OCI	19	(5)
Purchases	430	290
Settlements	(95)	(46)
Sales	(11)	(2)
Transfers into Level 3	73	6
Transfers out of Level 3	(148)	(47)
Ending balance	2,879	2,433
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Fair Value Option, Other Eligible Items \| Total Fixed Maturities, AFS
Assets
Beginning balance	197	167
Total realized/unrealized gains (losses), Included in net income	(4)	3
Total realized/unrealized gains (losses), Included in OCI	0	0
Purchases	6	0
Settlements	(4)	(3)
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	195	167
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| ABS \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	22	0
Total realized/unrealized gains (losses), Included in net income	0	0
Total realized/unrealized gains (losses), Included in OCI	1	0
Purchases	34	16
Settlements	(1)	0
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	56	16
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Collateralized Loan Obligations [Member] \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	116	113
Total realized/unrealized gains (losses), Included in net income	0	0
Total realized/unrealized gains (losses), Included in OCI	0	0
Purchases	208	130
Settlements	(1)	(12)
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(90)	(47)
Ending balance	233	184
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| CMBS \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	167	227
Total realized/unrealized gains (losses), Included in net income	0	0
Total realized/unrealized gains (losses), Included in OCI	3	10
Purchases	0	0
Settlements	0	(2)
Sales	(2)	0
Transfers into Level 3	35	6
Transfers out of Level 3	(53)	0
Ending balance	150	241
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| Corporate \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	2,281	1,861
Total realized/unrealized gains (losses), Included in net income	1	0
Total realized/unrealized gains (losses), Included in OCI	15	(15)
Purchases	164	106
Settlements	(89)	(27)
Sales	(9)	(2)
Transfers into Level 3	38	0
Transfers out of Level 3	0	0
Ending balance	2,401	1,923
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring \| RMBS \| Available-for-sale Securities [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	24	36
Total realized/unrealized gains (losses), Included in net income	0	0
Total realized/unrealized gains (losses), Included in OCI	0	0
Purchases	24	38
Settlements	(4)	(5)
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	(5)	0
Ending balance	$ 39	$ 69

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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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).

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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 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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Indicates line item in statement of income or comprehensive income that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

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