Investments - Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	$ 42,615	$ 41,102
Gross Unrealized Gains	1,022	652
Gross Unrealized Losses	2,995	4,056
Allowance for Credit Losses	16	1
Estimated Fair Value	40,626	37,697
Corporate bonds and other
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	25,020	23,137
Gross Unrealized Gains	597	301
Gross Unrealized Losses	1,345	2,009
Allowance for Credit Losses	4
Estimated Fair Value	24,268	21,429
States, municipalities and political subdivisions
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	7,713	8,918
Gross Unrealized Gains	382	338
Gross Unrealized Losses	703	939
Allowance for Credit Losses
Estimated Fair Value	7,392	8,317
Residential mortgage-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	3,411	3,073
Gross Unrealized Gains	16	5
Gross Unrealized Losses	425	447
Allowance for Credit Losses
Estimated Fair Value	3,002	2,631
Commercial mortgage-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	1,862	1,886
Gross Unrealized Gains	7	4
Gross Unrealized Losses	230	255
Allowance for Credit Losses	8
Estimated Fair Value	1,631	1,635
Other asset-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	3,515	3,287
Gross Unrealized Gains	13	2
Gross Unrealized Losses	256	361
Allowance for Credit Losses	4	1
Estimated Fair Value	3,268	2,927
Asset-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	8,788	8,246
Gross Unrealized Gains	36	11
Gross Unrealized Losses	911	1,063
Allowance for Credit Losses	12	1
Estimated Fair Value	7,901	7,193
U.S. Treasury and obligations of government-sponsored enterprises
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	152	111
Gross Unrealized Gains	1	1
Gross Unrealized Losses	2	2
Allowance for Credit Losses
Estimated Fair Value	151	110
Foreign government
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	741	617
Gross Unrealized Gains	6	1
Gross Unrealized Losses	34	43
Allowance for Credit Losses
Estimated Fair Value	713	575
Redeemable preferred stock
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost		3
Gross Unrealized Gains
Gross Unrealized Losses
Allowance for Credit Losses
Estimated Fair Value		3
Fixed maturities available-for-sale
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	42,414	41,032
Gross Unrealized Gains	1,022	652
Gross Unrealized Losses	2,995	4,056
Allowance for Credit Losses	16	1
Estimated Fair Value	40,425	37,627
Fixed maturities trading
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	201	70
Gross Unrealized Gains
Gross Unrealized Losses
Allowance for Credit Losses
Estimated Fair Value	$ 201	$ 70

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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