Investments - Available-for-sale Securities in Gross Unrealized Loss Position (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Estimated Fair Value
Total, Estimated Fair Value	$ 28,091	$ 25,731
Gross Unrealized Losses
Total, Gross Unrealized Losses	3,278	2,995
Fixed maturity securities
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	5,662	3,483
12 Months or Longer, Estimated Fair Value	22,429	22,248
Total, Estimated Fair Value	28,091	25,731
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	130	74
12 Months or Longer, Gross Unrealized Losses	3,148	2,921
Total, Gross Unrealized Losses	3,278	2,995
Corporate bonds and other
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	3,388	1,943
12 Months or Longer, Estimated Fair Value	13,395	13,406
Total, Estimated Fair Value	16,783	15,349
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	84	37
12 Months or Longer, Gross Unrealized Losses	1,412	1,308
Total, Gross Unrealized Losses	1,496	1,345
States, municipalities and political subdivisions
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	899	598
12 Months or Longer, Estimated Fair Value	3,257	3,104
Total, Estimated Fair Value	4,156	3,702
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	23	18
12 Months or Longer, Gross Unrealized Losses	777	685
Total, Gross Unrealized Losses	800	703
Residential mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	556	233
12 Months or Longer, Estimated Fair Value	2,227	2,212
Total, Estimated Fair Value	2,783	2,445
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	9	4
12 Months or Longer, Gross Unrealized Losses	486	421
Total, Gross Unrealized Losses	495	425
Commercial mortgage-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	170	200
12 Months or Longer, Estimated Fair Value	1,153	1,184
Total, Estimated Fair Value	1,323	1,384
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	1	5
12 Months or Longer, Gross Unrealized Losses	185	225
Total, Gross Unrealized Losses	186	230
Other asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	372	392
12 Months or Longer, Estimated Fair Value	1,904	1,869
Total, Estimated Fair Value	2,276	2,261
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	9	8
12 Months or Longer, Gross Unrealized Losses	251	248
Total, Gross Unrealized Losses	260	256
Total asset-backed
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	1,098	825
12 Months or Longer, Estimated Fair Value	5,284	5,265
Total, Estimated Fair Value	6,382	6,090
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	19	17
12 Months or Longer, Gross Unrealized Losses	922	894
Total, Gross Unrealized Losses	941	911
U.S. Treasury and obligations of government-sponsored enterprises
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	117	65
12 Months or Longer, Estimated Fair Value	51	23
Total, Estimated Fair Value	168	88
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	1	1
12 Months or Longer, Gross Unrealized Losses	2	1
Total, Gross Unrealized Losses	3	2
Foreign government
Estimated Fair Value
Less than 12 Months, Estimated Fair Value	160	52
12 Months or Longer, Estimated Fair Value	442	450
Total, Estimated Fair Value	602	502
Gross Unrealized Losses
Less than 12 Months, Gross Unrealized Losses	3	1
12 Months or Longer, Gross Unrealized Losses	35	33
Total, Gross Unrealized Losses	$ 38	$ 34