Investments - Available-for-sale Securities in Gross Unrealized Loss Position (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Estimated Fair Value
Total, Estimated Fair Value	$ 25,806	$ 27,288
Gross Unrealized Losses
Total, Gross Unrealized Losses	2,767	3,039
Fixed maturity securities
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	8,008	8,969
12 Months or Longer, Estimated Fair Value	17,798	18,319
Total, Estimated Fair Value	25,806	27,288
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	221	266
12 Months or Longer, Gross Unrealized Losses	2,546	2,773
Total, Gross Unrealized Losses	2,767	3,039
Corporate bonds and other
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	5,816	5,846
12 Months or Longer, Estimated Fair Value	9,986	10,388
Total, Estimated Fair Value	15,802	16,234
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	141	165
12 Months or Longer, Gross Unrealized Losses	1,008	1,140
Total, Gross Unrealized Losses	1,149	1,305
States, municipalities and political subdivisions
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	944	1,247
12 Months or Longer, Estimated Fair Value	2,986	2,967
Total, Estimated Fair Value	3,930	4,214
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	51	52
12 Months or Longer, Gross Unrealized Losses	778	783
Total, Gross Unrealized Losses	829	835
Total asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	1,100	1,709
12 Months or Longer, Estimated Fair Value	4,484	4,555
Total, Estimated Fair Value	5,584	6,264
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	26	45
12 Months or Longer, Gross Unrealized Losses	735	823
Total, Gross Unrealized Losses	761	868
Residential mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	413	849
12 Months or Longer, Estimated Fair Value	2,016	2,010
Total, Estimated Fair Value	2,429	2,859
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	9	22
12 Months or Longer, Gross Unrealized Losses	417	466
Total, Gross Unrealized Losses	426	488
Commercial mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	58	180
12 Months or Longer, Estimated Fair Value	969	988
Total, Estimated Fair Value	1,027	1,168
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	1	2
12 Months or Longer, Gross Unrealized Losses	118	139
Total, Gross Unrealized Losses	119	141
Other asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	629	680
12 Months or Longer, Estimated Fair Value	1,499	1,557
Total, Estimated Fair Value	2,128	2,237
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	16	21
12 Months or Longer, Gross Unrealized Losses	200	218
Total, Gross Unrealized Losses	216	239
U.S. Treasury and obligations of government-sponsored enterprises
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	43	49
12 Months or Longer, Estimated Fair Value	42	41
Total, Estimated Fair Value	85	90
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	1	1
12 Months or Longer, Gross Unrealized Losses	1
Total, Gross Unrealized Losses	2	1
Foreign government
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	105	118
12 Months or Longer, Estimated Fair Value	300	368
Total, Estimated Fair Value	405	486
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	2	3
12 Months or Longer, Gross Unrealized Losses	24	27
Total, Gross Unrealized Losses	$ 26	$ 30

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