Investments - Available-for-sale Securities in Gross Unrealized Loss Position (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Total, Estimated Fair Value	$ 24,701	$ 20,644
Total, Gross Unrealized Losses	2,568	2,286
Total fixed maturity securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	9,109	3,998
Less than 12 Months, Gross Unrealized Losses	182	79
12 Months or Longer, Estimated Fair Value	15,592	16,646
12 Months or Longer, Gross Unrealized Losses	2,386	2,207
Total, Estimated Fair Value	24,701	20,644
Total, Gross Unrealized Losses	2,568	2,286
Corporate bonds and other
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	6,698	2,776
Less than 12 Months, Gross Unrealized Losses	142	56
12 Months or Longer, Estimated Fair Value	7,903	8,576
12 Months or Longer, Gross Unrealized Losses	932	825
Total, Estimated Fair Value	14,601	11,352
Total, Gross Unrealized Losses	1,074	881
States, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	718	403
Less than 12 Months, Gross Unrealized Losses	12	8
12 Months or Longer, Estimated Fair Value	3,398	3,471
12 Months or Longer, Gross Unrealized Losses	781	734
Total, Estimated Fair Value	4,116	3,874
Total, Gross Unrealized Losses	793	742
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	365	154
Less than 12 Months, Gross Unrealized Losses	5	1
12 Months or Longer, Estimated Fair Value	1,882	2,002
12 Months or Longer, Gross Unrealized Losses	367	365
Total, Estimated Fair Value	2,247	2,156
Total, Gross Unrealized Losses	372	366
Commercial mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	126	36
Less than 12 Months, Gross Unrealized Losses	3	2
12 Months or Longer, Estimated Fair Value	825	887
12 Months or Longer, Gross Unrealized Losses	78	78
Total, Estimated Fair Value	951	923
Total, Gross Unrealized Losses	81	80
Other asset-backed
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	819	420
Less than 12 Months, Gross Unrealized Losses	13	9
12 Months or Longer, Estimated Fair Value	1,334	1,432
12 Months or Longer, Gross Unrealized Losses	206	185
Total, Estimated Fair Value	2,153	1,852
Total, Gross Unrealized Losses	219	194
Total asset-backed
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	1,310	610
Less than 12 Months, Gross Unrealized Losses	21	12
12 Months or Longer, Estimated Fair Value	4,041	4,321
12 Months or Longer, Gross Unrealized Losses	651	628
Total, Estimated Fair Value	5,351	4,931
Total, Gross Unrealized Losses	672	640
U.S. Treasury and obligations of government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	98	78
Less than 12 Months, Gross Unrealized Losses	2	2
12 Months or Longer, Estimated Fair Value	14	18
12 Months or Longer, Gross Unrealized Losses	1	1
Total, Estimated Fair Value	112	96
Total, Gross Unrealized Losses	3	3
Foreign government
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	285	131
Less than 12 Months, Gross Unrealized Losses	5	1
12 Months or Longer, Estimated Fair Value	236	260
12 Months or Longer, Gross Unrealized Losses	21	19
Total, Estimated Fair Value	521	391
Total, Gross Unrealized Losses	$ 26	$ 20