Fair Value Measurements - Fair Value Recurring Basis, Unobservable Input (Details) - Fair Value, Measurements, Recurring - Significant Unobservable Inputs (Level 3) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Assets
Beginning balance	$ 2,422	$ 2,445	$ 2,483	$ 2,708
Total realized/unrealized gains (losses), Included in net income	9	(3)	(9)	(7)
Total realized/unrealized gains (losses), Included in OCI	(23)	(56)	7	(242)
Purchases	197	146	420	846
Settlements	(100)	(58)	(241)	(329)
Sales	(1)	(11)	(15)	(33)
Transfers into Level 3	20	24	67	48
Transfers out of Level 3	(20)	(58)	(208)	(562)
Ending balance	2,504	2,429	2,504	2,429
Equity securities, at fair value
Assets
Beginning balance	59	60	61	64
Total realized/unrealized gains (losses), Included in net income	0	1	(2)	10
Total realized/unrealized gains (losses), Included in OCI	0	0	0	0
Purchases	0	0	1	2
Settlements	(1)	0	(2)	(15)
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance	58	61	58	61
Short-term investments
Assets
Beginning balance	186	60	193	80
Total realized/unrealized gains (losses), Included in net income	0	0	0	0
Total realized/unrealized gains (losses), Included in OCI	0	0	0	0
Purchases	2	36	6	72
Settlements	(3)	(3)	(14)	(9)
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	(50)
Ending balance	185	93	185	93
Securities available-for-sale and other \| Total Fixed Maturities, AFS
Assets
Beginning balance	2,014	2,132	2,051	2,404
Total realized/unrealized gains (losses), Included in net income	(4)	0	(7)	(2)
Total realized/unrealized gains (losses), Included in OCI	(23)	(56)	7	(242)
Purchases	195	110	413	717
Settlements	(93)	(52)	(220)	(291)
Sales	(1)	(11)	(15)	(33)
Transfers into Level 3	20	24	67	48
Transfers out of Level 3	(20)	(58)	(208)	(512)
Ending balance	2,088	2,089	2,088	2,089
Securities available-for-sale and other \| ABS \| Total Fixed Maturities, AFS
Assets
Beginning balance	0		30	0
Total realized/unrealized gains (losses), Included in net income	0		0	0
Total realized/unrealized gains (losses), Included in OCI	0		0	0
Purchases	46		82	19
Settlements	0		0	0
Sales	0		0	0
Transfers into Level 3	0		0	0
Transfers out of Level 3	0		(66)	(19)
Ending balance	46	0	46	0
Securities available-for-sale and other \| Collateralized Loan Obligations [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	85	164	115	257
Total realized/unrealized gains (losses), Included in net income	0	0	0	0
Total realized/unrealized gains (losses), Included in OCI	0	0	0	(2)
Purchases	15	31	55	113
Settlements	(3)	(13)	(33)	(53)
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(27)	(40)	(160)
Ending balance	97	155	97	155
Securities available-for-sale and other \| CMBS \| Total Fixed Maturities, AFS
Assets
Beginning balance	238	224	222	196
Total realized/unrealized gains (losses), Included in net income	0	0	(2)	0
Total realized/unrealized gains (losses), Included in OCI	1	(1)	3	(16)
Purchases	0	4	6	50
Settlements	(14)	(7)	(15)	(10)
Sales	0	0	(5)	0
Transfers into Level 3	1	0	17	0
Transfers out of Level 3	0	0	0	0
Ending balance	226	220	226	220
Securities available-for-sale and other \| Corporate \| Total Fixed Maturities, AFS
Assets
Beginning balance	1,622	1,609	1,589	1,618
Total realized/unrealized gains (losses), Included in net income	(4)	(1)	(5)	(2)
Total realized/unrealized gains (losses), Included in OCI	(24)	(52)	4	(210)
Purchases	113	75	230	398
Settlements	(69)	(13)	(150)	(145)
Sales	(1)	(9)	(10)	(30)
Transfers into Level 3	19	24	50	45
Transfers out of Level 3	(1)	(31)	(53)	(72)
Ending balance	1,655	1,602	1,655	1,602
Securities available-for-sale and other \| Foreign government/government agencies \| Total Fixed Maturities, AFS
Assets
Beginning balance		5		5
Total realized/unrealized gains (losses), Included in net income		1		0
Total realized/unrealized gains (losses), Included in OCI		0		(1)
Purchases		0		0
Settlements		0		0
Sales		(2)		(3)
Transfers into Level 3		0		3
Transfers out of Level 3		0		0
Ending balance		4		4
Securities available-for-sale and other \| RMBS \| Total Fixed Maturities, AFS
Assets
Beginning balance	69	130	95	328
Total realized/unrealized gains (losses), Included in net income	0	0	0	0
Total realized/unrealized gains (losses), Included in OCI	0	(3)	0	(13)
Purchases	21	0	40	137
Settlements	(7)	(19)	(22)	(83)
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(19)	0	(49)	(261)
Ending balance	64	108	64	108
Fair Value Option, Other Eligible Items \| Collateralized Loan Obligations [Member] \| Total Fixed Maturities, AFS
Assets
Beginning balance	163	193	178	160
Total realized/unrealized gains (losses), Included in net income	13	(4)	0	(15)
Total realized/unrealized gains (losses), Included in OCI	0	0	0	0
Purchases	0	0	0	55
Settlements	(3)	(3)	(5)	(14)
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance	$ 173	$ 186	$ 173	$ 186

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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- Definition

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
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- Definition

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
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-Name Accounting Standards Codification
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- Definition

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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- Definition

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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- Definition

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

+ References

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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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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