Investments - Available-for-sale Securities in Gross Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Estimated Fair Value
Total, Estimated Fair Value	$ 23,987	$ 27,288
Gross Unrealized Losses
Total, Gross Unrealized Losses	2,738	3,039
Fixed maturity securities
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	6,877	8,969
12 Months or Longer, Estimated Fair Value	17,110	18,319
Total, Estimated Fair Value	23,987	27,288
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	242	266
12 Months or Longer, Gross Unrealized Losses	2,496	2,773
Total, Gross Unrealized Losses	2,738	3,039
Corporate bonds and other
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	4,252	5,846
12 Months or Longer, Estimated Fair Value	9,515	10,388
Total, Estimated Fair Value	13,767	16,234
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	135	165
12 Months or Longer, Gross Unrealized Losses	934	1,140
Total, Gross Unrealized Losses	1,069	1,305
States, municipalities and political subdivisions
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	1,424	1,247
12 Months or Longer, Estimated Fair Value	2,938	2,967
Total, Estimated Fair Value	4,362	4,214
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	74	52
12 Months or Longer, Gross Unrealized Losses	818	783
Total, Gross Unrealized Losses	892	835
Total asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	1,001	1,709
12 Months or Longer, Estimated Fair Value	4,344	4,555
Total, Estimated Fair Value	5,345	6,264
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	27	45
12 Months or Longer, Gross Unrealized Losses	719	823
Total, Gross Unrealized Losses	746	868
Residential mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	372	849
12 Months or Longer, Estimated Fair Value	1,966	2,010
Total, Estimated Fair Value	2,338	2,859
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	9	22
12 Months or Longer, Gross Unrealized Losses	418	466
Total, Gross Unrealized Losses	427	488
Commercial mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	49	180
12 Months or Longer, Estimated Fair Value	959	988
Total, Estimated Fair Value	1,008	1,168
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses		2
12 Months or Longer, Gross Unrealized Losses	106	139
Total, Gross Unrealized Losses	106	141
Other asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	580	680
12 Months or Longer, Estimated Fair Value	1,419	1,557
Total, Estimated Fair Value	1,999	2,237
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	18	21
12 Months or Longer, Gross Unrealized Losses	195	218
Total, Gross Unrealized Losses	213	239
U.S. Treasury and obligations of government-sponsored enterprises
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	55	49
12 Months or Longer, Estimated Fair Value	19	41
Total, Estimated Fair Value	74	90
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	3	1
12 Months or Longer, Gross Unrealized Losses	2
Total, Gross Unrealized Losses	5	1
Foreign government
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	145	118
12 Months or Longer, Estimated Fair Value	294	368
Total, Estimated Fair Value	439	486
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	3	3
12 Months or Longer, Gross Unrealized Losses	23	27
Total, Gross Unrealized Losses	$ 26	$ 30

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