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
Mar. 31, 2021	Mar. 31, 2020
Fixed Maturities Available-for-Sale [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	$ 1,124	$ 633
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(11)	0
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	(51)	(46)
Purchases	72	112
Sales	0	0
Settlements	(19)	(5)
Transfers into Level 3	19	0
Transfers out of Level 3	(8)	(1)
Ending balance	1,126	693
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	0	0
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	(51)	(44)
Corporate Bonds and Other [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	770	468
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(13)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	(40)	(37)
Purchases	42	67
Settlements	(2)	(2)
Transfers into Level 3	10
Ending balance	767	496
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	(40)	(35)
States, Municipalities and Political Subdivisions [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	46
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	(2)
Ending balance	44
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	308	165
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	2
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	(9)	(9)
Purchases	30	45
Settlements	(17)	(3)
Transfers into Level 3	9
Transfers out of Level 3	(8)	(1)
Ending balance	315	197
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	(9)	(9)
Fixed Maturities Trading [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	8	4
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(3)	(1)
Ending balance	5	3
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	(3)	(1)
Total Fixed Maturities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	1,132	637
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	(14)	(1)
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in OCI	(51)	(46)
Purchases	72	112
Sales	0	0
Settlements	(19)	(5)
Transfers into Level 3	19	0
Transfers out of Level 3	(8)	(1)
Ending balance	1,131	696
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	(3)	(1)
Unrealized gains (losses) recognized in other comprehensive income (loss) on level 3 assets and liabilities	(51)	(44)
Equity Securities [Member]
Reconciliations for All Assets and Liabilities [Roll Forward]
Beginning balance	43	19
Net realized investment gains (losses) and net change in unrealized investment gains (losses), included in net income	2	(3)
Ending balance	45	16
Unrealized gains (losses) recognized in net income (loss) on level 3 assets and liabilities	$ 2	$ 3

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
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-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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