Investments - Amortized Cost and Fair Values of Fixed Maturity Securities (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	$ 43,113	$ 42,615
Gross Unrealized Gains	843	1,022
Gross Unrealized Losses	3,096	2,995
Allowance for Credit Losses	20	16
Estimated Fair Value	40,840	40,626
Corporate and other bonds
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	25,221	25,020
Gross Unrealized Gains	485	597
Gross Unrealized Losses	1,374	1,345
Allowance for Credit Losses	3	4
Estimated Fair Value	24,329	24,268
States, municipalities and political subdivisions
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	7,726	7,713
Gross Unrealized Gains	318	382
Gross Unrealized Losses	756	703
Allowance for Credit Losses
Estimated Fair Value	7,288	7,392
Residential mortgage-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	3,563	3,411
Gross Unrealized Gains	10	16
Gross Unrealized Losses	483	425
Allowance for Credit Losses
Estimated Fair Value	3,090	3,002
Commercial mortgage-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	1,838	1,862
Gross Unrealized Gains	8	7
Gross Unrealized Losses	193	230
Allowance for Credit Losses	8	8
Estimated Fair Value	1,645	1,631
Other asset-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	3,586	3,515
Gross Unrealized Gains	19	13
Gross Unrealized Losses	251	256
Allowance for Credit Losses	9	4
Estimated Fair Value	3,345	3,268
Asset-backed
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	8,987	8,788
Gross Unrealized Gains	37	36
Gross Unrealized Losses	927	911
Allowance for Credit Losses	17	12
Estimated Fair Value	8,080	7,901
U.S. Treasury and obligations of government-sponsored enterprises
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	181	152
Gross Unrealized Gains		1
Gross Unrealized Losses	2	2
Allowance for Credit Losses
Estimated Fair Value	179	151
Foreign government
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	763	741
Gross Unrealized Gains	3	6
Gross Unrealized Losses	37	34
Allowance for Credit Losses
Estimated Fair Value	729	713
Fixed maturities available-for-sale
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	42,878	42,414
Gross Unrealized Gains	843	1,022
Gross Unrealized Losses	3,096	2,995
Allowance for Credit Losses	20	16
Estimated Fair Value	40,605	40,425
Fixed maturities trading
Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract]
Cost or Amortized Cost	235	201
Gross Unrealized Gains
Gross Unrealized Losses
Allowance for Credit Losses
Estimated Fair Value	$ 235	$ 201

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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