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	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fixed Maturities Available-for-Sale [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	$ 1,126	$ 693	$ 1,124	$ 633
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	4	0	(7)	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	22	77	(29)	32
Purchases	218	39	290	151
Sales	(3)	(9)	(3)	(9)
Settlements	(33)	(9)	(52)	(15)
Transfers into Level 3	21	0	40	0
Transfers out of Level 3	(5)	(14)	(13)	(15)
Ending balance	1,350	777	1,350	777
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	0	0	0
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	22	76	(29)	34
Corporate Bonds and Other [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	767	496	770	468
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	3		(10)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	16	59	(24)	22
Purchases	122	4	164	71
Sales	(3)		(3)
Settlements	(22)	(4)	(24)	(6)
Transfers into Level 3			10
Ending balance	883	555	883	555
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	16	58	(24)	24
States, Municipalities and Political Subdivisions [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	44		46
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	2
Purchases	12		12
Settlements	(1)		(1)
Ending balance	57		57
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	2
Asset-Backed [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	315	197	308	165
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1		3
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	4	18	(5)	10
Purchases	84	35	114	80
Sales		(9)		(9)
Settlements	(10)	(5)	(27)	(9)
Transfers into Level 3	21		30
Transfers out of Level 3	(5)	(14)	(13)	(15)
Ending balance	410	222	410	222
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	4	18	(5)	10
Fixed Maturities Trading [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	5	3	8	4
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(3)	1	(6)
Settlements	(2)		(2)
Ending balance		4		4
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities		1
Total Fixed Maturities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	1,131	696	1,132	637
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1	1	(13)	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	22	77	(29)	32
Purchases	218	39	290	151
Sales	(3)	(9)	(3)	(9)
Settlements	(35)	(9)	(54)	(15)
Transfers into Level 3	21	0	40	0
Transfers out of Level 3	(5)	(14)	(13)	(15)
Ending balance	1,350	781	1,350	781
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	1	0	0
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	22	76	(29)	34
Equity Securities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	45	16	43	19
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(15)	(4)	(13)	(7)
Purchases	10		10
Sales	(4)		(4)
Transfers into Level 3		15		15
Ending balance	$ 36	27	36	27
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities		$ (4)	$ 2	$ (7)

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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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).

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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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