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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fixed Maturities Available-for-Sale [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	$ 1,350	$ 777	$ 1,124	$ 633
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	2	0	(5)	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	2	14	(27)	45
Purchases	138	194	428	345
Sales	(9)	0	(12)	(9)
Settlements	(22)	(17)	(74)	(31)
Transfers into Level 3	41	8	81	8
Transfers out of Level 3	(90)	(2)	(103)	(17)
Ending balance	1,412	974	1,412	974
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	2	13	(27)	48
Corporate Bonds and Other [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	883	555	770	468
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1		(9)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	1	5	(23)	27
Purchases	55	129	219	200
Sales			(3)
Settlements	(11)	(3)	(35)	(9)
Transfers into Level 3		8	10	8
Transfers out of Level 3	(52)		(52)
Ending balance	877	694	877	694
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	2	5	(22)	29
States, Municipalities and Political Subdivisions [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	57	0	46	0
Purchases		45	12	45
Settlements			(1)
Ending balance	57	45	57	45
Asset-Backed [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	410	222	308	165
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	1		4
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	1	9	(4)	18
Purchases	83	20	197	100
Sales	(9)		(9)	(9)
Settlements	(11)	(14)	(38)	(22)
Transfers into Level 3	41		71
Transfers out of Level 3	(38)	(2)	(51)	(17)
Ending balance	478	235	478	235
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities		8	(5)	19
Fixed Maturities Trading [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	0	4	8	4
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income		4	(6)	4
Settlements			(2)
Ending balance	0	8	0	8
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities		4		4
Total Fixed Maturities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	1,350	781	1,132	637
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	2	4	(11)	4
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	2	14	(27)	45
Purchases	138	194	428	345
Sales	(9)	0	(12)	(9)
Settlements	(22)	(17)	(76)	(31)
Transfers into Level 3	41	8	81	8
Transfers out of Level 3	(90)	(2)	(103)	(17)
Ending balance	1,412	982	1,412	982
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	4	0	4
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	2	13	(27)	48
Equity Securities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	36	27	43	19
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(2)		(15)	(7)
Purchases	1	12	11	12
Sales	(11)		(15)
Transfers into Level 3	11		11	15
Transfers out of Level 3	(10)		(10)
Ending balance	25	$ 39	25	39
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	$ (3)		$ (1)	$ (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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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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